Reactivity of hydroxy- and aquo(hydroxy)-λ3-iodane-crown ether complexes.

We have designed a series of hydroxy(aryl)-λ(3)-iodane-[18]crown-6 complexes, prepared from the corresponding iodosylbenzene derivatives and superacids in the presence of [18]crown-6, and have investigated their reactivities in aqueous media. These activated iodosylbenzene monomers are all non-hygroscopic shelf-storable reagents, but they maintain high oxidizing ability in water. The complexes are effective for the oxidation of phenols, sulfides, olefins, silyl enol ethers, and alkyl(trifluoro)borates under mild conditions. Furthermore, hydroxy-λ(3)-iodane-[18]crown-6 complexes serve as efficient progenitors for the synthesis of diaryl-, vinyl-, and alkynyl-λ(3)-iodanes in water. Other less polar organic solvents, such as methanol, acetonitrile, and dichloromethane, are also usable in some cases.


Time-Lapse Fluorescence Imaging and Quantitative Single Cell and Endosomal Analysis of Peritoneal Macrophages Using Fluorescent Organosilica Nanoparticles

Fluorescent thiol-organosilica nanoparticles with 100 nm diameter (F-thiol-OS-100) were applied for time-lapse fluorescence imaging. The evaluation of F-thiol-OS-100 for quantitative analysis demonstrated great advantages as compared with quantum dots and organic fluorescent dye. Time-lapse fluorescence imaging of mouse peritoneal macrophages using F-thiol-OS-100 clearly demonstrated cellular uptake, and single cell analysis showed various patterns of uptake kinetics that could be quantitatively evaluated. We also performed quantitative analysis of endosomal uptake and movements in single cells. A correlation between morphologic findings and endosomal uptake and movement over time was also observed and analyzed quantitatively. The F-thiol-OS-100 showed high potential as a new fluorescence marker for time-lapse fluorescence imaging and quantitative single cell functional analysis for nanomedicine development. In this study the authors report on 100 nm thiol-organosilica nanoparticles as time-lapse flurescent markers. F-thiol-OS-100 proved to be superior to quantum dots and organic flurescent dyes, and enabled quantitative single cell functional analysis.

Nanomedicine : Nanotechnology, Biology, and Medicine


In Situ Generation Technology of β-Butoxycarbonyliodonium Ylide: A Hypervalent Analogue of the Darzens Reagent


Metal-free α-CH amination of ethers with hypervalent sulfonylimino-λ3-bromane that acts as an active nitrenoid.

Hypervalent N-triflylimino-λ(3)-bromane undergoes direct and regioselective α-C-H amination of ethers at room temperature under transition metal-free conditions. Kinetic results, substituent and deuterium isotope effects suggest an asynchronous concerted organonitrenoid transition state with some hydride transfer character, analogous to that for alkane C-H insertions.


A catalytic version of hypervalent aryl-λ3-iodane-induced Hofmann rearrangement of primary carboxamides: iodobenzene as an organocatalyst and m-chloroperbenzic acid as a terminal oxidant

The first catalytic version of hypervalent aryl-λ(3)-iodane-induced Hofmann rearrangement of primary carboxamides, which probably involves in situ generation of a tetracoordinated bis(aqua)(hydroxy)phenyl-λ(3)-iodane complex as an active oxidant from a catalytic amount of iodobenzene by the reaction with m-chloroperbenzoic acid in the presence of HBF(4) in dichloromethane-water under mild conditions, was developed.


Synthesis and Structure of Hypervalent Diacetoxybromobenzene and Aziridination of Olefins with Imino-λ3-bromane Generated in Situ under Metal-Free Conditions

Ligand exchange of p-CF(3)C(6)H(4)BrF(2) with acetoxy groups using AcOH and Ac(2)O affords (diacetoxybromo)benzene in a high yield, which undergoes aziridination of alkenes in the presence of TfNH(2) and sulfamate esters in one pot under mild conditions. The aziridination with TfNH(2) proceeds stereospecifically with retention of stereochemistry of olefins at room temperature using limiting amounts of olefins under transition-metal-free conditions. The one-pot aziridination procedure using sulfamate esters can be applied to the intramolecular versions.


Oxidation of Primary Aliphatic and Aromatic Aldehydes with Difluoro(aryl)-λ3-bromane

Oxidation of primary aliphatic aldehydes with p-trifluoromethylphenyl(difluoro)-λ(3)-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses.


Highly Regioselective Amination of Unactivated Alkanes by Hypervalent Sulfonylimino-λ3-Bromane

Amination of alkanes has generally required metal catalysts and/or high temperatures. Here we report that simple exposure of a broad range of alkanes to N-triflylimino-λ(3)-bromane 1 at ambient temperature results in C-H insertion of the nitrogen functionality to afford triflyl-substituted amines in moderate to high yields. Marked selectivity for tertiary over secondary C-H bonds was observed; primary (methyl) C-H bonds were inert. Addition of hexafluoroisopropanol to inhibit decomposition of 1 dramatically improved the C-H amination efficiencies. Second-order kinetics, activation parameters (negative activation entropy), deuterium isotope effects, and theoretical calculations suggest a concerted asynchronous bimolecular transition state for the metal-free C-H amination event.


Synthesis and Structure of Aliphatic Phenylchloronium Ylide


Weakly Nucleophilic Conjugate Bases of Superacids as Powerful Nucleophiles in Vinylic Bimolecular Nucleophilic Substitutions of Simple β-Alkylvinyl(aryl)-λ3-bromanes

We report herein, for the first time, the stereoselective synthesis of simple (E)-β-alkylvinyl(aryl)-λ(3)-bromanes via a boron-λ(3)-bromane exchange reaction and their unique bimolecular nucleophilic substitutions at the vinylic ipso carbon atom under mild conditions. Interestingly, even weakly nucleophilic anions such as conjugate bases of superacids (HBF(4), TfOH, Tf(2)CH(2), Tf(3)CH, Tf(2)NH, etc.) function as nucleophiles toward the vinyl-λ(3)-bromanes. For instance, the vinylic S(N)2 reaction of (E)-vinyl-λ(3)-bromanes with potassium bis(triflyl)methanide stereoselectively produced (Z)-vinyloxy oxosulfonium ylides with exclusive inversion of configuration via oxygen attack, while that with potassium bis(triflyl)imide afforded predominantly (Z)-vinyloxysulfoximines. In marked contrast, (E)-β-alkylvinyl-λ(3)-iodanes do not undergo the vinylic S(N)2 reaction with these conjugate bases of superacids. The differences between the nucleofugalities of aryl-λ(3)-iodanyl and aryl-λ(3)-bromanyl groups (the latter being greater) probably play a pivotal role in these unique reactions.

Journal of the American Chemical Society


Hypervalent phenyl-λ3-iodane-mediated para-selective aromatic fluorination of 3-phenylpropyl ethers

Exposure of 3-phenylpropyl ethers to an activated iodosylbenzene monomer·18-crown-6 complex [PhI(OH)BF(4)·18C6] in the presence of BF(3)-Et(2)O and water results in the para-selective monofluorination of benzene ring via neighboring alkoxy group participation and directly affords 3-(4-fluorophenyl)propyl ethers regioselectively in good yields.


Hypervalent N-sulfonylimino-λ3-bromane: active nitrenoid species at ambient temperature under metal-free conditions

The synthesis and reactions of N-triflylimino-lambda(3)-bromane are summarized. The hypervalent iminobromane functions as a highly active nitrenoid species at ambient temperature under transition metal-free conditions, probably because of the increased hypernucleofugality of aryl-lambda(3)-bromanyl groups compared to that of aryl-lambda(3)-iodanyl groups. The imino-lambda(3)-bromane undergoes stereospecific aziridination of olefins and transylidation to aromatic nitrogen heterocycles, trialkylamines and iodobenzenes. Difluoro-lambda(3)-bromane-induced Hofmann rearrangement of primary arylsulfonamides is also discussed.


Imination of Sulfides and Sulfoxides with Sulfonylimino-λ3-Bromane under Mild, Metal-Free Conditions

Exposure of sulfides and sulfoxides to trifluoromethanesulfonylimino(aryl)-lambda(3)-bromane in dichloromethane at 0 degrees C results in a facile transfer of the sulfonylimino group to sulfur atoms and affords N-triflylsulfilimines and -sulfoximines in high yields under transition-metal-free conditions. Imination of (R)-methyl p-tolyl sulfoxide proceeded with predominant retention of configuration at the stereogenic sulfur center. The Hammett plot afforded rho values of -0.58 for para-substituted thioanisoles and -0.49 for their equivalent sulfoxides, which suggests a buildup of positive charge on the sulfur atoms of sulfides and sulfoxides in the transition state. Calculations suggest a bimolecular nucleophilic-substitution mechanism on the negatively charged nitrogen atom of the sulfonylimino-lambda(3)-bromane, which involves the attack of a sulfide from the opposite side to bromine(III).


Hypervalent λ3-Bromane Strategy for Baeyer-Villiger Oxidation: Selective Transformation of Primary Aliphatic and Aromatic Aldehydes to Formates, Which is Missing in the Classical Baeyer-Villiger Oxidation,

A conceptually distinct, modern strategy for Baeyer-Villiger oxidation (BVO) was developed. Our novel method involves initial hydration of water to carbonyl compounds, followed by ligand exchange of hypervalent aryl-lambda(3)-bromane on bromane(III) with the resulting hydrate, yielding a new type of activated Criegee intermediate. The intermediate undergoes BV rearrangement and produces an ester via facile reductive elimination of an aryl-lambda(3)-bromanyl group, because of the hypernucleofugality. The novel strategy makes it possible to induce selectively the BV rearrangement of straight chain primary aliphatic as well as aromatic aldehydes, which is missing in the classical BVO: for instance, octanal and benzaldehyde afforded rearranged formate esters with high selectivity (>95%) under our conditions, while the attempted classical BVO produced only carboxylic acids. This firmly establishes the powerful nature of new methodology for BVO.


Effects of stereochemistry and β-substituents on the rates of vinylic SN2 reaction of hypervalent vinyl(phenyl)-λ3-iodanes with tetrabutylammonium halides


Facile Generation of a Strained Cyclic Vinyl Cation by Thermal Solvolysis of Cyclopent-1-enyl-λ3-bromanes


Difluoro-λ3-bromane-Induced Hofmann Rearrangement of Sulfonamides: Synthesis of Sulfamoyl Fluorides

We report the first example of Hofmann rearrangement of primary arenesulfonamides, which relies on the use of p-trifluoromethylphenyl(difluoro)-lambda(3)-bromane and affords N-arylsulfamoyl fluorides selectively at room temperature. Reaction of aryl-lambda(3)-iodanes with p-toluenesulfonamide affords sulfonylimono-lambda(3)-iodanes, being excellent progenitors for generation of metal-nitrenoid species. In marked contrast, reaction of the difluoro-lambda(3)-bromane with p-toluenesulfonamide in benzene produced unique N-p-tolylsulfamoyl fluoride in a high yield, through Hofmann rearrangement. Arenesulfonamides with electron-donating (p-MeO and o-Me) and -withdrawing substituents (p-F, p-Cl, and p-CF(3)) efficiently undergoes the lambda(3)-bromane-induced Hofmann rearrangement. The structure of N-p-tolylsulfamoyl fluoride was determined by a single-crystal X-ray analysis. The differences in nucleofugality between aryl-lambda(3)-iodanyl and aryl-lambda(3)-bromanyl groups, the later being greater, probably play a pivotal role in determining the reaction course. The results obtained from the reaction of 2,3,5,6-tetramethylbenzenesulfonamide strongly suggest that generation of sulfonyl nitrene will not be involved in this rearrangement.


Oxidation of Benzyl Alcohols with Difluoro(aryl)-λ3-bromane: Formation of Benzyl Fluoromethyl Ethers via Oxidative Rearrangement


Direct Transfer of the Sulfonylimino Group of Imino-λ3-Bromane to N-Heterocycles and Trialkylamines: Synthesis of N-Iminoammonium Ylides under Metal-Free Conditions

Exposure of N-heterocycles and aliphatic trialkylamines to trifluoromethanesulfonylimino-lambda(3)-bromane at room temperature results in direct transfer of the sulfonylimino group to the nitrogen atoms and affords a variety of iminoammonium ylides under transition-metal-free conditions. The imino-lambda(3)-bromane probably serves as an active nitrenoid species without any activation and produces the ammonium ylides via a bimolecular nucleophilic substitution process.


Imido transfer of sulfonylimino-λ3-bromane makes possible the synthesis of sulfonylimino-λ3-iodanes

Sulfonylimino-lambda(3)-bromane functions as a reactive nitrenoid, because of the hyperleaving group ability of aryl-lambda(3)-bromanyl groups, and undergoes transimidations to iodobenzenes at room temperature under metal-free conditions probably via an S(N)2-type nitrenoid transition state, yielding sulfonylimino-lambda(3)-iodanes.


Iodomesitylene-Catalyzed Oxidative Cleavage of Carbon-Carbon Double and Triple Bonds Using m-Chloroperbenzoic Acid as a Terminal Oxidant

Transition metal-catalyzed oxidative cleavage of carbon-carbon multiple bonds has emerged as a powerful tool in organic synthesis. High-valent oxometals, mostly of Ru, Os, Mn, Mo, W, and Re, were used catalytically as reactive oxygen transfer agents to the multiple bonds. Reported here for the first time are the organocatalytic versions of the oxidative cleavage reactions. Our method involves use of iodomesitylene as an effective organocatalyst, which generates an active aryl(hydroxy)-lambda(3)-iodane 5 in situ, and m-chloroperbenzoic acid (m-CPBA) as a terminal oxidant under metal-free conditions. Cyclic and acyclic olefins as well as aliphatic and aromatic alkynes were smoothly cleaved to carboxylic acids under the organocatalytic conditions.

Journal of the American Chemical Society


Catalytic Version of and Reuse in Hypervalent Organo λ3- and λ5-iodane Oxidation.


Thermal and Catalytic Transylidations between Halonium Ylides and Synthesis and Reaction of Stable Aliphatic Chloronium Ylides.


A New Type of Imido Group Donor: Synthesis and Characterization of Sulfonylimino-λ3-bromane that Acts as a Nitrenoid in the Aziridination of Olefins at Room Temperature under Metal-Free Conditions


Internal Delivery of Soft Chlorine and Bromine Atoms: Stereoselective Synthesis of (E)-beta-Halogenovinyl(aryl)-lambda3-iodanes through Domino lambda3-Iodanation-1,4-Halogen Shift-Fluorination of Alkynes

4-(Difluoroiodo)toluene-induced domino lambda(3)-iodanation-1,4-halogen shift-ring enlargement-fluorination reaction of 5-halopentynes with a four-, five-, or six-membered carbocycle afforded the ring-expanded (E)-delta-fluoro-beta-halovinyl-lambda3-iodanes stereoselectively in high yields, probably via the intermediacy of five-membered halonium ions. Use of internal alkynes makes it possible to synthesize tetrasubstituted beta-halovinyl-lambda(3)-iodanes with defined stereochemistry.


One-Pot Regioselective Synthesis of Chromanyl(phenyl)-lambda3-iodanes: Tandem Oxidative Cyclization and lambda3-Iodanation of 3-Phenylpropanols

Reaction of 3-phenylpropanol with an activated iodosylbenzene-18-crown-6 complex [PhI(OH)BF4-18C6] in dichloromethane in the presence of BF3-Et2O afforded directly the 6-chromanyl(phenyl)-lambda3-iodane-18C6 complex through tandem oxidative intramolecular cyclization yielding chroman and its regioselective phenyl-lambda3-iodanation.


Activated Iodosylbenzene Monomer as an Ozone Equivalent: Oxidative Cleavage of Carbon-Carbon Double Bonds in the Presence of Water


trans Influences on Hypervalent Bonding of Aryl lambda3-Iodanes: Their Stabilities and Isodesmic Reactions of Benziodoxolones and Benziodazolones


Synthesis and Characterization of Bromonium Ylides and Their Unusual Ligand Transfer Reactions with N-Heterocycles

Stable aliphatic bromonium ylides (RfSO2)2C--Br+C6H4-p-CF3 (Rf = CF3, CF3(CF2)3) have been synthesized and structurally characterized for the first time. X-ray crystallographic analyses indicated a ylide structure with an sp2 hybridization of the ylide carbanions and with little double-bond character for the ylidic bond. The bromonium ylides selectively undergo transfer of the aryl group to nitrogen heterocycles, such as pyridines, yielding N-arylpyridinium salts. This is in a marked contrast to the reaction of the iodonium ylides, which produces pyridinium ylides through transylidations.


Silver Technology for Stabilization of Simple (Z)-Enethiols: Stereoselective Synthesis and Reaction of Silver (Z)-Enethiolates

Reported here for the first time are the stereoselective synthesis and reaction of simple silver (Z)-enethiolates, which serve as stabilized (Z)-enethiol storage. In contrast to labile enethiols, silver (Z)-enethiolates are stable even in solutions, and their isolation and purification are very simple. The method for synthesis of silver (Z)-enethiolates involves an unusual vinylic SN2 reaction of (E)-vinyl-lambda3-iodanes with thiobenzamides yielding the inverted (Z)-S-vinylthioimidonium salts, followed by their regioselective C-S bond cleavage with silver acetate. Alkylation, arylation, and Michael addition of silver (Z)-enethiolates yielding (Z)-vinyl sulfides were dramatically accelerated by the addition of Bu4NI (LiI), which probably generates reactive ammonium (Z)-enethiolates with an increased nucleophilicity.


Photochemical Generation of Six- and Five-Membered Cyclic Vinyl Cations

The photochemical solvolyses of 4-tert-butylcyclohex-1-enyl(phenyl)iodonium tetrafluoroborate (1) and cyclopent-1-enyl(phenyl)iodonium tetrafluoroborate (2) in methanol yield vinylic ethers and vinylic cycloalkenyliodobenzenes and cycloalkenylbenzene, which are the trapping products of the geometrically destabilized C6-ring and C5-ring vinyl cation with the solvent and with the leaving group iodobenzene. Iodonium salt 2 also yields an allylic ether and allylic cyclopentenyliodobenzenes and cyclopentenylbenzene, which are the trapping products of the C5-ring allylic cation produced from the C5-ring vinyl cation by a hydride shift in a typical carbocationic rearrangement.


Complexation of Diphenyl(tetrafluoroborato)-lambda3-iodane with Pyridine


Synthesis, Characterization, and Reaction of Crown Ether Complexes of Aqua(hydroxy)(aryl)iodonium Ions


Thiazole Synthesis by Cyclocondensation of 1-Alkynyl(phenyl)-λ3-iodanes with Thioureas and Thioamides


Domino Michael addition-carbene rearrangement-cyclization reaction of 1-alkynyl(aryl)-λ3-bromanes with 2-mercapto-1,3-benzazoles

Exposure of 1-alkynyl[p-(trifluoromethyl)phenyl](tetrafluoroborato)-lambda3-bromanes to 2-mercaptobenzimidazole or benzothiazole in dichloromethane at 0 degrees C under argon resulted in a domino Michael addition-carbene rearrangement-cyclization reaction to produce directly tricyclic heterocycles in high yields, whereas the reaction with 2-mercaptobenzoxazole afforded 1-alkynyl sulfides.


Iodobenzene-Catalyzed α-Acetoxylation of Ketones. In Situ Generation of Hypervalent (Diacyloxyiodo)benzenes Using m-Chloroperbenzoic Acid

Reported here for the first time is the iodobenzene-catalyzed alpha-oxidation of ketones, in which diacyloxy(phenyl)-lambda3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3.Et2O, and water at room temperature under argon affords an alpha-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer-Villiger oxidation of a ketone took place. It is noted that use of water and BF3.Et2O is crucial to the success of this alpha-acetoxylation.

Journal of the American Chemical Society


Synthesis and Characterization of β-Haloalkenyl-λ3-bromanes: Stereoselective Markovnikov Addition of Difluoro(aryl)-λ3-bromane to Terminal Acetylenes

Reported here for the first time are the synthesis, isolation, and characterization of hypervalent beta-haloalkenyl-lambda3-bromanes. Exposure of terminal alkynes to p-trifluoromethylphenyl(difluoro)-lambda3-bromane activated by BF3-i-Pr2O resulted in fluoro-lambda3-bromanation of the triple bonds in a Markovnikov fashion, yielding (E)-beta-fluoroalkenyl-lambda3-bromanes stereoselectively in good yields. 5-Chloro-1-pentynes undergo domino lambda3-bromanation-chlorine shift-fluorination or lambda3-bromanation-chlorine shift-alkyl shift-fluorination reaction, depending on the substituents and afford (E)-beta-chloroalkenyl-lambda3-bromanes stereoselectively in high yields. The beta-chloroalkenyl-lambda3-bromanes contain three kinds of halogen atoms, F, Cl, and Br, in the molecule.


Effects of Complexation with 18-Crown-6 on the Hypernucleofugality of Phenyl-λ3-iodanyl Groups. Synthesis of Vinyl-λ3-iodane·18-Crown-6 Complex

[structure: see text] 4-tert-Butyl-1-cyclohexenyl(phenyl)(tetrafluoroborato)-lambda(3)-iodane forms a discrete supramolecular complex by the reaction with 18-crown-6. Solvolysis of the cyclohexenyl-lambda(3)-iodane in the presence of 18-crown-6 indicates that the complexation with 18-crown-6 tends to decrease the leaving group ability of hypervalent phenyl-lambda(3)-iodanyl groups.


1-Alkyl(aryl)(tetrafluoroborate)-λ3-bromanes as highly efficient Michael acceptors: Uncatalyzed conjugate addition of 1-alkynyl(trialkyl)stannanes yielding symmetrical and unsymmetrical 1,3-butadiynes


Addition to Electron Deficient Olefins of α-Oxy Carbon-Centered Radicals,Generated from Cyclic Ethers and Acetals by the Reaction with Alkylperoxy-λ3-iodane


Tandem Michael addition carbene insertion reaction of 1-alkynyl(aryl)(tetrafluoroborato)-λ3-bromanes: 1-(phenylsulfonyl)- and 1-(trifluoromethylsulfonyl)cyclopentene annulation

Exposure of 1-alkynyl[p-(trifluoromethyl)phenyl](tetrafluoroborato)-lambda(3)-bromanes to sodium benzenesulfinate or sodium trifluoromethanesulfinate in dichloromethane at 0 degree C under argon resulted in tandem Michael-carbene insertion reactions to produce 1-sulfonylcyclopentenes selectively, with concomitant formation of a small amount of rearranged 1-alkynyl sulfones.


Oxidation of 3-Hydroxypiperidines with Iodosylbenzene in Water: Tandem Oxidative Grob Fragmentation-Cyclization Reaction

Oxidation of 3-hydroxypiperidine with iodosylbenzene in water afforded 2-pyrrolidinone directly in good yields. The reaction probably involves oxidative Grob fragmentation yielding imino aldehyde, which upon hydrolysis produces 2-pyrrolidinone via a cyclization-oxidation sequence.


Reaction of Unstabilized Iodonium Ylides with Organoboranes


Tetrahydrofuranylation of alcohols catalyzed by alkylperoxy-λ3-iodane and carbon tetrachloride


Synthesis, structure, and reaction of 1-alkynyl(aryl)-lambda3-bromanes

Reported here for the first time are the synthesis, structure, and reaction of hypervalent 1-alkynyl(aryl)-lambda3-bromanes. BF3-catalyzed ligand exchange on bromine(III) of p-trifluoromethylphenyl(difluoro)-lambda3-bromane with 1-alkynyl(trimethyl)stannanes in dichloromethane at -78 degrees C afforded 1-alkynyl(aryl)-lambda3-bromanes in good yields. Trimethyl(trimethylsilylethynyl)stannane gave silylethynyl-lambda3-bromane selectively. 13C NMR chemical shifts of acetylenic carbon atoms of alkynylbromanes are compared with those of alkynyl-lambda3-iodanes and explained in terms of the spin-orbit-induced heavy atom effects. The structure of tert-butylethynylbromane was established by a single-crystal X-ray analysis of its crown ether complex. The 1-alkynyl(aryl)-lambda3-bromanes serve as highly electron-deficient Michael acceptors and undergo tandem Michael-carbene rearrangements by the reaction with sulfonate anions, yielding 1-alkynyl sulfonates.


Synthesis and structure of supramolecular complexes between 1-alkynyl(phenyl)(tetrafluoroborato)-λ3-iodanes and 18-crown-6


Isolation, Characterization, and Reaction of Activated Iodosylbenzene Monomer Hydroxy(phenyl)iodonium Ion with Hypervalent Bonding: Supramolecular Complex PhI+OH·18-Crown-6 with Secondary I···O Interactions

The isolation, characterization, and reaction of the active species hydroxy(phenyl)iodonium ion with hypervalent bonding are reported. Reaction of iodosylbenzene with HBF(4)-Me(2)O in the presence of equimolar 18-crown-6 in dichloromethane afforded the hydroxy-lambda(3)-iodane complex PhI(OH)BF(4).18-crown-6 as stable yellow prisms. X-ray structure analysis indicated that both the close contacts between the iodine(III) and the three adjacent oxygen atoms of 18-crown-6, and the hydrogen bonding OH.O(crown ether) will be responsible for the increased stability of the complex as compared to the uncomplexed PhI(OH)BF(4). The crown ether complex is highly reactive and serves as a versatile oxidant even in water: thus, the complex undergoes oxidative transformations of a variety of functional groups such as olefins, alkynes, enones, silyl enol ethers, sulfides, and phenols under mild conditions.

Journal of the American Chemical Society


Synthesis of 2,4-Disubstituted Thiazoles from (Z)-(2-Acetoxyvinyl)phenyl-λ3-iodanes: Nucleophilic Substitution of α-λ3-Iodanyl Ketones with Thioureas and Thioamides

In the presence of triethylamine, (Z)-(2-acetoxy-1-alkenyl)phenyl-lambda(3)-iodanes react with thioureas or thioamides in MeOH to give 2,4-disubstituted thiazoles directly in good yields. The reaction probably involves generation of highly reactive alpha-lambda(3)-iodanyl ketones through ester exchange of the beta-acetoxy group with liberation of methyl acetate, followed by nucleophilic substitutions with thioureas or thioamides.


Borane-induced radical reduction of 1-alkenyl- and 1-alkynyl-λ3-iodanes with tetrahydrofuran


Solid state structures of pentacoordinated λ3-iodanes with a trigonal bipyramidal geometry: synthesis of diphenyl- and alkynyl(phenyl)-λ3-iodane complexes with 1,10-phenanthroline

The single crystal X-ray structure of the supramolecular complex formed between diphenyl-lambda3-iodane (Ph2IBF4) or 1-alkynyl(phenyl)-lambda3-iodane [Bu(t)CCI(Ph)BF4] and 1,10-phenanthroline indicates a hitherto unknown distorted trigonal bipyramidal geometry around iodine(III), in which 1,10-phenanthroline acts as a bidentate ligand and occupies equatorial sites.


Synthesis, Characterization, and Reaction of Ethynyl(phenyl)-λ3-Iodane Complex with [18]Crown-6


Synthesis of 1-alkynyl(diphenyl)onium salts of group 16 elements via heteroatom transfer reaction of 1-alkynyl(phenyl)-λ3-iodanes

1-Alkynyl(phenyl)-lambda 3-iodanes undergo selective transfer of the alkynyl groups over the phenyl group onto diphenyl chalcogens. Exposure of 1-alkynyl(phenyl)-lambda 3-iodanes to diphenyl chalcogens (S, Se, and Te) in dichloromethane or 1,2-dichloroethane affords 1-alkynyl(diphenyl)sulfonium, -selenonium, and -telluronium salts in high yields.


Secondary hypervalent I(III) ---O interactions: Synthesis and structure of hypervalent complexes of diphenyl-<lambda>^3-iodanes with 18-crown-6

Reported here for the first time are the synthesis and characterization of supramolecular complexes between diaryl-lambda(3)-iodanes and 18-crown-6 (18C6). Slow evaporation of solvents afforded 1:1 and 2:1 complexes between Ph(2)IBF(4) and 18C6 as stable crystals, depending on the conditions. X-ray crystal structures of these complexes indicated that each iodine atom contacts with the three adjacent oxygen atoms of 18C6 through two hypervalent secondary bonding and a weak interaction. (1)H NMR analyses and CSI-MS spectra showed that, in dichloromethane solution, Ph(2)IBF(4) exclusively forms the 1:1 complex with 18C6 (binding constant K(a), 1.02 x 10(3) M(-)(1)). The binding constants decrease with the increased solvent donor ability (Gutmann's DN). Changing the heteroatom ligand from BF(4) to the less nucleophilic PF(6) and AsF(6) increased the binding constant by about six times. Substitution of an electron-withdrawing group onto the para position of Ph(2)IBF(4) tends to increase in the complex stability. A linear Hammett relationship (rho = 0.59) between log K(a) and sigma(p)(+) values of substituents indicates that the diaryl-lambda(3)-iodanes with electropositive iodine(III) interact more efficiently with 18C6. Decreased binding magnitude was measured with 15C5, dibenzo-18C6, dibenzo-21C7, and dibenzo-30C10.


On the mechanism of α-phenylation of β-keto esters with diaryl-λ3-iodanes: evidence for a non-radical pathway


Vinyl-λ3-iodanes act as efficient sulfur atom acceptors: vinylic SN2-based strategy for conversion of tertiary thioamides to amides

Exposure of tertiary thioamides to (E)-1-hexenyl(phenyl)-lambda 3-iodane results in vinylic SN2 reaction to give the inverted (Z)-S-vinylthioimidonium salts, which under alkaline hydrolysis (Na2CO3 or K2CO3) selectively afford amides, while (Z)-S-vinyl thioesters are obtained in high yields via the hydrolysis under acidic conditions (HCl).


A New Route for Generation of α-λ3-Iodanyl Ketones via Ester Exchange of (Z)-(β-Acetoxyvinyl)-λ3-iodanes: Their Nucleophilic Substitutions with Halides and Sulfur and Phosphorus Nucleophiles

An efficient method for generation of alpha-lambda3-iodanyl ketones from (Z)-(2-acetoxyvinyl)(phenyl)-lambda3-iodanes was developed. The method involves ester exchange of (Z)-2-acetoxyvinyl-lambda3-iodanes with methanol in the presence of triethylamine. alpha-lambda3-Iodanyl ketones react with a variety of nucleophiles such as halides, thiols, phosphines, phosphinic acids, and phosphates, under the conditions which produce alpha-functionalized carbonyl compounds probably via an S(N)2 pathway.


Thermal and Photochemical Solvolysis of (E)- and (Z)-2-Phenyl-1-propenyl(phenyl)iodonium Tetrafluoroborate: Benzenium and Primary Vinylic Cation Intermediates

The thermal and photochemical solvolysis of the two stereoisomeric 2-phenyl-1-propenyl(phenyl)iodonium tetrafluoroborates has been investigated in alcoholic solvents of varying nucleophilicity. The product profiles and rates of product formation in the thermal reaction are all compatible with a mechanism involving cleavage of the vinylic C-I bond assisted by the group in the trans position (methyl or phenyl), always leading to rearranged products. Depending on the nucleophilicity of the solvent, the primarily formed cations may or may not further rearrange to more stable isomers. The less reactive Z compound also yields some unrearranged vinyl ether product in the more nucleophilic solvents via an in-plane S(N)2 mechanism. The mechanism of the photolysis involves direct, unassisted cleavage of the vinylic, and aromatic, C-I bond in an S(N)1 mechanism. This produces a primary vinyl cation, which is partially trapped prior to rearrangement in methanol. The unrearranged vinyl ethers are mainly formed with retention of configuration via a lambda3-iodonium/solvent complex in an S(N)i mechanism. Thermal and photochemical solvolyses of iodonium salts are complementary techniques for the generation of different cation intermediates from the same substrate.

Journal of the American Chemical Society


Stereoselective Synthesis of (Z)-Enethiols and Their Derivatives: Vinylic SN2 Reaction of (E)-Alkenyl(phenyl)-λ3-iodanes with Thioamides

[reaction: see text]. Exposure of (E)-beta-alkylvinyl(phenyl)-lambda3-iodanes to thioamides in dichloromethane at room temperature was found to result in a bimolecular nucleophilic substitution (S(N)2) at the vinylic carbon atom to give inverted (Z)-enethiols and/or (Z)-S-vinylthioimidonium salts. Vinylic S(N)2 reactions with thioureas are also discussed.


Oxidative Ring Cleavage of Cyclic Acetals with Hypervalent tert-Butylperoxy-λ3-iodanes


Reactions of 2,2-Dialkylvinyl Iodonium Salt with Halide Ions

Bulletin of the Chemical Society of Japan


Unprecedented Direct Oxygen Atom Transfer from Hypervalent Oxido-λ3-iodanes to α,β-Unsaturated Carbonyl Compounds: Synthesis of α,β-Epoxy Carbonyl Compounds


Triphenylphosphine-mediated olefination of aldehydes with (Z)-(2-acetoxyalk-1-enyl)phenyl-λ3-iodanes: generation and reaction of (2-oxoalkyl)phenyl-λ3-iodanes

Journal of the Chemical Society. Chemical Communications


Solvolysis of 2,2-Dialkylvinyl Iodonium Salt: Alkyl Participation and Possibility of a Primary Vinylic Cation Intermediate


Onium Transfer Reaction of (β,β-Dialkylvinyl)(phenyl)iodonium Tetrafluoroborates via an Alkylidene Carbene Pathway: Synthesis of Group 15 Alkenyl(triphenyl)- and Group 16 Alkenyl(diphenyl)onium Salts


Synthesis of Chiral Diaryliodonium Salts, 1,1'-Binaphthyl-2-yl(phenyl)iodonium Tetrafluoroborates: Asymmetric α-Phenylation of β-Keto Ester Enolates


Chromium(II)-Mediated Reactions of Iodonium Tetrafluoroborates with Aldehydes: Umpolung of Reactivity of Diaryl-, Alkenyl(aryl)-, and Alkynyl(aryl)iodonium Tetrafluoroborates

The method described herein allows us, for the first time, to perform umpolung of reactivity of diaryl-, alkenyl(aryl)-, and alkynyl(aryl)iodonium tetrafluoroborates. The method involves generation of organochromium(III) species via reaction of iodonium salts with anhydrous chromium dichloride, followed by their nucleophilic addition to aldehydes to yield alcohols. In contrast to the reaction of aryl and alkenyl halides with chromium dichloride, these iodonium salts are so active that organochromium(III) could be generated without using a nickel catalyst. Substituent effects of unsymmetrically substituted diaryliodonium salts on the product profiles are in good agreement with the reported mode of decomposition of the intermediate unsymmetrical diaryliodanyl radicals. Alkenyl(mesityl)iodonium tetrafluoroborates undergo exclusive alkenylation of aldehydes with no signs of the formation of an arylation product.


Radical oxidation of amides and related compounds with hypervalent tert-butylperoxyiodanes: Synthesis of imides and tert-butylperoxyamide acetals


Aziridination of Activated Imines with Monocarbonyl Iodonium Ylides Generated from (Z)-(2-Acetoxyvinyl)iodonium Salts via Ester Exchange: Stereoselective Synthesis of 2-Acylaziridines

Monocarbonyl iodonium ylides, generated in situ from (Z)-(2-acetoxyvinyl)iodonium salts via an ester exchange reaction with EtOLi, undergo alkylidene transfer reactions to activated imines yielding 2-acylaziridines in good yields. The stereochemical outcome of this aziridination was shown to be dependent on both the activating groups of the imines and the reaction solvents: that is, the aziridination of N-(2,4,6-trimethylbenzenesulfonyl)imines in THF affords cis-aziridines as a major product while that of N-benzoylimines in THF-DMSO or THF gives the trans isomer stereoselectively.


Solvolysis of Styryliodonium Salt: Products, Rates, and Mechanisms


Association and dissociation of Z-(<beta>-bromoalkenyl)-phenyliodonium bromide in chloroform solution: Detection of vinyl-<lambda>^3-iodane dimer in solution


Formamides undergo in-plane bimolecular nucleophilic vinylic substitutions (SN2) by the reaction with (E)-alkenyl(phenyl)iodonium tetrafluoroborates: stereoselective synthesis of (Z)-vinyl formates


Solvolysis of β,β-Dialkylvinyliodonium Salt: Primary Vinyl Cation Intermediate and Alkyl Participation


On the mechanism of nucleophilic substitution of allenyl(aryl)iodine(III): Formation of propargyl cation and competition with sigmatropic rearrangement


Reactions of Phenyl(styryl)iodonium Tetrafluoroborate with Halide Ions

Bulletin of the Chemical Society of Japan


Reaction of monocarbonyl iodonium ylides with activated imines: Stereoselective synthesis of trans- and cis-α,β-aziridino ketones


In-Plane Vinylic SN2 Substitution and Intramolecular β Elimination of β-Alkylvinyl(chloro)-λ3-iodanes

Journal of the American Chemical Society


Vinylic SN 2 Reaction of 1-Decenyliodonium Salt with Halide Ions


Oxidation of Amines with Hypervalent tert-Butylperoxyiodanes: Synthesis of Imines and tert-Butylperoxyamino Acetals


Generation and Reaction of Monocarbonyliodonium Ylides: Ester Exchange of (Z)-(β-Acetoxyvinyl)iodonium Salts with Lithium Ethoxide and Synthesis of α,β-Epoxy Ketones


The first example for reactivity umpolung of diaryliodonium salts: Chromium(II)-mediated arylation of aldehydes


Nucleophilic Vinylic Substitutions of (Z)-(β-Haloalkenyl)phenyliodonium Salts with Sodium Benzenesulfinate: First Evidence of a Michael Addition of Nucleophiles to Alkenyliodonium Salts at the Cβ Atom


Stereospecific Synthesis of Vinyl(phenyl)iodonium Tetrafluoroborates via Boron-Iodane Exchange of Vinylboronic Acids and Esters with Hypervalent Phenyliodanes


Ligand Coupling Mechanism of Nucleophilic Vinylic Substitution of Iodonium Salts with Hypervalent 10-I-3 and 12-I-4 Intermediates


Oxidation of Sulfides to Sulfoxides with Hypervalent (tert-Butylperoxy)iodanes

Oxidation of sulfides with the crystalline (alkylperoxy)iodanes, 1-(tert-butylperoxy)-1,2-benziodoxol-3(1H)-ones 2a and 2b, in acetonitrile-water or in dichloromethane, affords sulfoxides in high yields. Measurement of the relative rates of oxidation for a series of ring-substituted thioanisoles 3b (p-MeO), 3c (p-Me), and 3d (p-Cl) in acetonitrile-water indicates that electron-releasing groups such as p-MeO and p-Me groups increase the rate of oxidation, and Hammett correlation of the relative rate factors with the substituent constants affords the reaction constants rho(+) = -2.23 (sigma(+), r = 0.98) for BF(3)-catalyzed oxidation and rho = -3.32 (sigma, r = 0.98) for uncatalyzed oxidation. The effects of a free-radical scavenger, galvinoxyl, were examined. A mechanism involving the intermediary formation of the sulfonium species 11 by nucleophilic attack of sulfide toward the iodine(III) atom of 2 is proposed for the oxidation in acetonitrile-water in the presence and the absence of BF(3). Et(2)O. On the other hand, the oxidation of sulfoxides in dichloromethane probably proceeds by a radical process, which involves the decomposition at room temperature of 2 via homolytic bond cleavage of the weak iodine(III)-peroxy bond, generating tert-butylperoxy radical and the [9-I-2] iodanyl radical 12.


Free-radical oxidation of para-substituted phenols by hypervalent tert-butylperoxyiodane and tert-butyl hydroperoxide: Synthesis of 4-(tert-butylperoxy)-2,5-cyclohexadien-1-ones


Acetolysis of Styryl and 1-Decenyl Iodonium Salts. Occurrence of Two-Step Mechanism via Vinylenephenonium Ion and One-Step Inversion Mechanism


α-Vinylation of 1,3-Dicarbonyl Compounds with Alkenyl(aryl)iodonium Tetrafluoroborates: Effects of Substituents on the Aromatic Ring and of Radical Inhibitors


Boron-iodine(III) exchange reaction: Direct synthesis of diaryliodonium tetraarylborates from (diacetoxyiodo)arenes by the reaction with alkali metal tetraarylborates in acetic acid


Direct synthesis of 2-substituted furotropones from tropolones utilizing alkynyl(phenyl)iodonium salts


Alcoholysis of Epoxides Catalyzed by Tetracyanoethylene and Dicyanoketene Acetals

Bulletin of the Chemical Society of Japan


Synthesis and nucleophilic substitution of allenyl-(m-nitrophenyl)iodanes as anewpropynyl cation-equivalent species: Synthesis of propynyl ethers, esters, and amides


Hypervalent (tert-butylperoxy)iodines generate iodine-centered radicals at room temperature in solution: Oxidation and de-protection of benzyl and allyl ethers, and evidence for generation of <alpha>-oxy carbon radicals

Journal of the American Chemical Society


Evidence for reversible ylide formation: Equilibrium between free alkylidenecarbenes and ethereal solvent-alkylidenecarbene complexes (oxoniumu ylides)


Nature of Alkylidenecarbenes Generated from Alkenyl(phenyl)iodonium Tetrafluoroborates via Base-Induced α-Elimination


Solvent Effects on Ipso versus Ortho Selectivity in the Reductive Iodonio-Claisen Rearrangement of Allenyl(p-methoxyphenyl)iodane


Solvolysis of Cyclohexenyliodonium Salt, a New Precursor for the Vinyl Cation: Remarkable Nucleofugality of the Phenyliodonio Group and Evidence for Internal Return from an Intimate Ion-Molecule Pair


An onium transfer reaction of 1-alkynyl(phenyl)iodonium tetrafluoroborates with triphenylarsine; Synthesis of 1-alkynyl(triphenyl)arsonium tetrafluoroborates


Different Mechanisms of Action of Long Chain Fatty Acid Esters of Podophyllotoxin and


Biomimetic, Chemical, and Spectroscopic Evaluations for the Radiosensitizing Potential of


Radiosensitizing Hypoxic Cells with New 3-Nitro-1,2,4-triazole Derivatives in Vitro and


Effect of Oridonin, a Rabdosia Diterpenoid, on Radiosensitization with Misonidazole


Synthetic Development of Hypoxic Cell Sensitizers Having 3-Nitrotriazole Moiety


Evaluation of the Affinity of New N Atom-Containing Tumor Inhibitors for Nucleic Acids

Nucleic Acids Research, Symposium Series