Rhodium-catalyzed alkynylation of carbon-carbon unsaturated bonds giving hydroalkynylation products took place in high yields with high stereoselectivity. Selective hydroalkynylation of internal alkynes with silylacetylenes giving 1, 3-enynes was realized by use of a hydroxorhodium catalyst. Asymmetric 1, 3-rearrangement of an alkynyl group of alkynyl alkenyl carbinols giving β-alkynylketones took place in high yields with high enantioselectivity in the presence of a hydroxorhodium/(R)-binap catalyst, which includes a key β-alkynyl elimination step in the cat-alytic cycle. Rhodium-catalyzed asymmetric conjugate alkynylation of α, β-unsaturated ketones giving β-alkynylketones was realized by use of (triisopropylsilyl) acetylene combined with (R)-DTBM-segphos as a chiral phosphine ligand, where the sterically bulky substituents on the silicon and phosphorus atoms suppress the alkyne dimerization. It was found that the presence of an acid was essential in the rhodium-catalyzed asymmetric addition of terminal alkynes to diarylphosphinylallenes giving exo-enynes in high yields with high regio- and enantioselectivity, where the stereochemical outcome is determined at the protonolysis of the π-allylrhodium(I) intermediate involved in the catalytic cycle.
New fundamental reactions of organometallic compounds can often be a rich source of new synthetic reactions. We found σ-bond metathesis of M-X bonds in group 11 metal compounds with Si-H, Si-Si and B-B bonds. Through these reactions, several intermediates such as borylcopper(I), silylcopper(I), gold(I) hydride species, which otherwise are not easily accessible, can be generated and incorporated into catalytic reactions.We report a novel and versatile method for the synthesis of allylboronates through γ-selective substitution of allylic carbonates with diboron in the presence of a Cu (I)-phosphine catalyst. The Cu(I)-catalyzed reaction includes formal nucleophilic reaction of borylcopper(I) intermediates to allylic carbonates. The approach involving the reaction of borylcopper(I) intermediates has been further expanded to enantioselective synthesis of both optically active α-chiral allylboronates and B, Si-bifunctional cyclopropanes.Copper(I) catalysis based on a-bond metathesis of hydrosilanes and disilanes with copper(I) complex offers new synthetic methods for various organosilanes. Gold(I) catalysis involving gold (I) hydride species is also reported.
New synthetic reactions which involve the formation of unsaturated titanacycles are described. The reaction of carbene complexes of titanium, generated from thioacetals or gem-dichlorides, with alkynes produced titanacyclobutenes. Hydrolysis or β-hydride elimination of these titanacycles gave a variety of alkenes and dienes. When alkynyl sulfones were employed, β-elimination of the initially formed 3-sulfonyltitanacyclobutenes produced allenyltitanium species which gave homopropargylic alcohols on treatment with carbonyl compounds. Titanacyclobutenes with different substitution patterns were also produced by the reductive titanation of γ-chloroallylic sulfides with titanocene-triethylphosphite complex. The formation of titanacyclopentenes by the reaction of alkenes bearing a leaving group such as vinyl pivalate and (Z)-alkenyl sulfones, alkynes, and the titanocene(II) reagent, and the subsequent β-elimination constitute useful methods for the vinylation and E-selective alkenylation of alkynes. Carbonyl compounds were also transformed into allylic alcohols when treated with the same reagent system. The alkenylation of alkynyl sulfones and subsequent reductive titanation of the resulting α-sulfonyldienyltitanium species generated titanium-alkenylalkenylidene complexes which reacted with carbonyl compounds to produce various alkenylallenes with complete stereoselectivity.
Preparation, surface modification of mesoporous silica, and its application to the polymer synthesis were reviewed. The template synthesis of mesoporous materials by using surfactants and block copolymers were first introduced. The surface modification within the mesoporous interior was classified into two type reactions: Cocondensation of tetraalkoxysilane with functional molecules having silane coupling parts. The Grignard reagent-utilized functionalization of mesoporous material was also introduced with the analysis of the functionalization efficiency by IR spectroscopy. The application of the functionalized mesoporous materials to the polymer synthesis, especially controlled synthesis, was introduced.
Recent progress in crystal engineering and crystallography has revealed many features of organic reactions performed in the solid state. The direct observation of a continuous change in the crystal structures of reactant molecules during the reactions in the crystalline state can give us valuable information. In this review article, we describe our recent studies on the mechanism of the solid-state organic reactions including EZ-photoisomerization, [2 + 2] photodimerization, and topochemical polymerization of muconic esters as the 1, 3-diene monomers. The direct observation of molecular motion in the crystals during single crystal-to-single crystal transformation opens a new insight for understanding the mechanism of solid-state reactions and also the design of new functional solid materials.
Self-assembly and nanostructure formation of tetrathiafulvalene (TTF) oligomers using S and π-π interactions are summarized. Thus, tris(TTF)-annulenes were prepared by palladium-catalyzed couplings of diethynyl-TTFs. Multi-functional TTF-annulenes show various chromic properties in solution and the nanofiber formation in the solid state. Interestingly, the diamagnetic responsibility of the annulene can be employed for the fiber alignment in a magnetic field. Fur-thermore, flexible star-shaped TTF oligomers were prepared by Sonogashira coupling of iodo-TTF with ethynylbenzenes. The star-shaped TTFs show strong self-aggregation in solution. In the case of the star-shaped hexamer, hexagonally ordered one-dimensional nanofibers are constructed both in neutral and cationic states. The electric conductivity of the cation-radical fiber is 2 orders of magnitude higher than that of the cation-radical film.
? The catalytic decomposition of diazo compounds and the subsequent insertion of a carbene group into the C-H bond constitute one of the very few examples of effective catalytic functionalization of hydrocarbons. This transformation has been achieved with rhodium-, copper-, silver- and gold-based catalysts under mild conditions. Recently, the catalytic carbenoid insertion in non-conventional media has attracted attention, because such reactions offer more environmental-ly friendly organic synthetic methodologies. In this review, recent reports on this topic will be summarized.