Published papers

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-λ3-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. Copyright © 2006 American Chemical Society.

The single crystal X-ray structure of the supramolecular complex formed between diphenyl-λ3-iodane (Ph2IBF4) or 1-alkynyl(phenyl)-λ3-iodane [ButCCI(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. © 2003 Royal Society of Chemistry.

Slow evaporation of a solution of 1-decynyl(phenyl)(tetrafluoroborato)-lambda(3)-iodane and 18-crown-6 in dichloromethane-diethyl ether-hexane gave a supramolecular 1:1 complex, while 3,3-dimethyl-1-butynyl- and phenylethynyl(phenyl)(tetrafluoroborato)-lambda(3)-iodanes afforded 2:1 complexes. Complexation with 18-crown-6 increased the thermal stability of the phenylethynyl-lambda(3)-iodane. Solid state and solution structures of these complexes were examined by single crystal X-ray analyses, H-1 and C-13 NMR spectra, and cold-spray ionization MS. Binding constants were measured by H-1 NMR titrations. (C) 2003 Elsevier Ltd. All rights reserved.

1-Alkynyl(phenyl)-λ3-iodanes undergo selective transfer of the alkynyl groups over the phenyl group onto diphenyl chalcogens. Exposure of 1-alkynyl(phenyl)-λ3-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.

Iodine(III) crowned: Slow evaporation of solvents afforded the 1:1 complex 1 between [H-C≡C-I-Ph]BF4 and [18]crown-6 (18C6). Both the solid-state and solution structures of 1 were determined. Reaction of 1 with methanol proceeds in a Michael-type fashion. The complexation with 18C6 increases the stability of labile λ3-iodanes, such as 1.

Intermolecular transylidation between halonium ylides under thermal and catalytic (rhodium (II) acetate) conditions, which makes it possible to synthesize a hitherto unknown kind of aliphatic chloronium ylides as well as a variety of bromonium and iodonium ylides, was developed. The uncatatyzed thermal transylidations of bromonium to iodonium ylides probably involve generation of a reactive carbene :C(SO2CF3)(2), being electrophilic in nature. Compared to the bromonium and iodonium ylides, the chloronium ylide serves as a much better progenitor for generation of carbenes; (or carbenoids) and efficiently undergoes cyclopropanation of olefins such as cyclooctadiene under uncatatyzed thermal conditions. A greater leaving group ability of the lambda(3)-chloranyl and lambda(3)-bromanyl groups compared to that of the lambda(3)-iodanyl group seems to be responsible for the observed differences in reactivity between these halonium ylides.

(Chemical Equation Presented) The isolation and intramolecular cyclization of (S)-(1-alkynyl)isothiouronium and (S)-(1-alkynyl)thiobenzimidonium salts suggest the mechanism for the one-pot synthesis of 2,4-disubstituted thiazoles (see scheme; Ms = methanesulfonyl): Michael addition of sulfur nucleophiles to hypervalent iodanes followed by the 1,2-rearrangement of sulfenyl groups in the resulting alkylidene carbenes. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA.

Large and small or twice moderate: Both combinations of trans influences of the substituents favor the formation of highly stable aryl λ 3-iodanes ArILL' (examples: PhI(OH)OTs and PhI(OAc)2). trans influences also seem to explain why iodosylbenzene adopts an oxo-bridged zigzag polymer structure in contrast to PhI(OH)2, which is monomeric. (Chemical Equation Presented). © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

The first catalytic version of hypervalent aryl-λ3-iodane-induced Hofmann rearrangement of primary carboxamides, which probably involves in situ generation of a tetracoordinated bis(aqua)(hydroxy)phenyl-λ3-iodane complex as an active oxidant from a catalytic amount of iodobenzene by the reaction with m-chloroperbenzoic acid in the presence of HBF4 in dichloromethane–water under mild conditions, was developed. © 2012 The Royal Society of Chemistry.

A facile and divergent synthetic process for converting tertiary allylic alcohols to multiply substituted allylic boronates is reported. This methodology is especially effective for tertiary alcohol substrates, providing the corresponding allylic boronates in moderate to good yields.

Conjugation between σ- and π-aromatic moieties in 1-C-arylated monocarba-closo-dodecaborate anion derivatives 2 has been identified by means of kinetic experimental studies combined with theoretical calculations. We found that the reaction rate of iodination at the 12-B vertex of the carborane anion cage was affected by distal substituents on the benzene ring connected at the antipodal carbon vertex. Hammett and Yukawa-Tsuno plots indicated that substantial resonance effects are involved. Density functional theory calculations enabled detailed interpretation of the electronic interaction.

Various aryl-, alkenyl-, and/or alkyllithium species reacted smoothly with aryl and/or benzyl ethers with cleavage of the inert C-O bond to afford cross-coupled products, catalyzed by commercially available [Ni(cod)(2)] (cod=1,5-cyclooctadiene) catalysts with N-heterocyclic carbene (NHC) ligands. Furthermore, the coupling reaction between the aryllithium compounds and aryl ammonium salts proceeded under mild conditions with C-N bond cleavage in the presence of a [Pd(PPh3)(2)Cl-2] catalyst. These methods enable selective sequential functionalizations of arenes having both C-N and C-O bonds in one pot.

We present an allylic polyfluoroarylation reaction with broad substrate scope and excellent functional group tolerance, using organozinc reagents under mild conditions. A catalytic amount of triphenylphosphine oxide efficiently promotes iodine-zinc exchange reaction between polyfluoroaryl iodide and dimethylzinc, and the resulting phosphine oxide-activated polyfluoroarylzinc undergoes substitution reaction with allylic halides to afford the corresponding polyfluoroarylated products. (C) 2015 Elsevier Ltd. All rights reserved.

Deprotonative directed ortho cupration of aromatic/heteroaromatic C-H bond and subsequent oxidation with t-BuOOH furnished functionalized phenols in high yields with high regio- and chemoselectivity. DFT calculations revealed that this hydroxylation reaction proceeds via a copper (I → III → I) redox mechanism. Application of this reaction to aromatic C-H amination using BnONH2 efficiently afforded the corresponding primary anilines. These reactions show broad scope and good functional group compatibility. Catalytic versions of these transformations are also demonstrated.

We describe an efficient regioselective formation of six-/seven-membered cyclic ethers based on goldcatalyzed intramolecular hydroalkoxylation. Sequential gold-catalyzed cyclization and palladium-catalyzed cross-coupling reactions afforded 6,6-bicyclic ethers, while reversing the reaction sequence (cross-coupling then cyclization) afforded 6,7-bicyclic ethers. This methodology should provide access to a range of functional polycyclic ethers.

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-δ3-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.

Exposure of 3-phenylpropyl ethers to an activated iodosylbenzene monomer·18-crown-6 complex [PhI(OH)BF4·18C6] in the presence of BF3–Et2O 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. © 2011 The Royal Society of Chemistry.

An in vitro imaging system to evaluate the stealth function of nanoparticles against mouse macrophages was established using fluorescent organosilica nanoparticles. Surface-functionalized organosilica nanoparticles with polyethylene glycol (PEG) were prepared by a one-step process, resulting in a brush-type PEG layer. A simultaneous dual-particle administration approach enabled us to evaluate the stealth function of nanoparticles with respect to single cells using time-lapse fluorescent microscopic imaging and flow cytometry analyses. Single-cell imaging and analysis revealed various patterns and kinetics of bare and PEGylated nanoparticle uptake. The PEGylated nanoparticles revealed a stealth function against most macrophages (PEG-sensitive macrophages); however, a stealth function against certain macrophages (PEG-insensitive macrophages) was not observed. We identified and characterized the PEG-resistant macrophages that could take up PEGylated nanoparticles at the same level as bare nanoparticles.

An ester exchange reaction of β-butoxy-β-acyloxyvinyl- λ3-iodane with lithium bases (ROLi and nBuLi) efficiently generates highly labile monoester iodonium ylide at low temperature. The iodonium ylide generated in situ cleanly undergoes Darzens condensation with aromatic aldehydes to afford trans-epoxy ester selectively. The reactivity of monoester iodonium ylide is investigated. Highly labile mono ester iodonium ylide generated in situ from β-butoxy-β-acyloxyvinyl- λ3-iodane through an ester exchange reaction cleanly undergoes Darzens-type condensation with aromatic aldehydes to afford trans-epoxy ester selectively. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.