After a brief historical survey of organosilicon chemistry, the latest developments in this area are reviewed. Selected topics are : stereochemistry and mechanisms of nucleophilic substitutions at silicon; asymmetric syntheses of organosilicon compounds; organofluorosilanes and -fluorosilicates; utilization of the “disilane fraction” produced by the direct synthesis of methylchlorosilanes; organopolysilanes; silyl metal compounds; silicon-containing small ring systems; divalent silicon species; double-bonded silicon species; and silicon in organic synthesis.
Tetrakis (trimethylsilyl) ethylene and 1, 1-bis (t-butyldimethylsilyl) -2, 2-bis (trimethylsilyl) ethylene are very crowded olefins with double bonds twisted by 29.6 and 49.6°, respectively. Other related tetrasilylethylenes also show interesting physical and chemical properties due to overcrowding. For example, the energy barrier of E/Z isomerization around the double bond of 1, 2-bis (phenyldimethylsilyl) -1, 2-bis (trimethylsilyl) ethylene is 29.7 kcal·mol-1 Spectra and reactions of these compounds are discussed.
Some of our recent studies on the photochemical formation and reactions of silacyclopropenes are described. The silacyclopropenes can readily be obtained by two different methods, the reaction of phenyl (trimethylsilyl) silylene generated by photolysis of tris (trimethylsilyl) phenylsilane with alkynes, and photochemical isomerization of phenylethynyl-and trimethylsilylethynyldisilane derivatives. Photochemical and thermal behavior of these silacyclopropenes are discussed. The reaction of the silacyclopropenes produced from phenylethynyldisilanes with phenyl-(silyl) acetylenes in the presence of dichlorobis (triethylphosphine) nickel (II) affords siloles in high yields, while the palladium-catalyzed reaction gives 1, 4-disilacyclohexa-2, 5-dienes.
This review article deals with recent advances in silicon-carbon bond forming reactions. The topics are discussed in the following four items : (1) standard methods (e. g., direct synthesis, transmetallation, and hydrosilylation); (2) silicon-carbon bond formation of a new type (e. g., reductive silylation and reaction of a silyl anion or silylene); (3) new silylations with disilanes (e. g., double silylation and dehalogenative silylation); (4) miscellaneous reactions.
Transition metal catalyzed reaction of olefins with hydrosilanes to give vinylsilanes is reviewed. Dodecacarbonyltriruthenium is an efficient catalyst of the dehydrogenative silylation. The mechanism of the reaction is discussed.
The reactions of allylsilanes are discussed in terms of the allyl anion equivalents, the allyl cation equivalents, and olefins. The reactions concerning with the latter two were developed recently by the authors. The major discussion is focused on these new type reactions.
This article describes the regiospecific phenylselenodesilylation of allylsilanes and the synthetic application of allylsilanes as potent synthons of allylic alcohol skeletons. 2- or 3-bromoallyltrimethylsilanes are represented to give the novel reagents for the introduction of allylic alcohol skeletons to several electrophiles by way of formation of allylselenide or allylsulfide and subsequent oxidative rearrangement.
Silylated synthons-synthesized by great variety of silylation reaction-are widely used as precousors to synthesize variety of organic compounds. This review describes recent porgress of silylation techniques and some of fields of use for silylated synthons.
Trialkylsilyl triflates are a new class of super-reagents, which act as efficient agents for silylation of active hydrogen compounds and catalysts of nucleophilic addition and displacement reactions in aprotic media. The synthetic utility is exemplified by a variety of functional group transformations and carbon-carbon bond-forming reactions. Immobilization of the silyl reagent on a resinsulfonic acid is also described.
Iodotrimethylsilane which has a hard acid (Me3Si) -soft base (I) bond displays a strong oxygenophilicity towards ethers, esters, lactones, acetals, and other molecules involving oxygen atom as a functional group. Recent progress of the chemistry of iodotrimethylsilane is reviewed especially from a view point of organic synthesis. The application of bromotrimethylsilane to organic synthesis is also discussed briefly.
Syntheses of phosphoenolpyruvate and ascorbic acid 2-O-phosphate have been done by use of the silyl phosphate intermediates. The silyl esters were converted smoothly to the corresponding phosphates by simple alcoholysis under very mild conditions.
Intramolecular Diels-Alder reactions of o-quinodimethane intermediates provide an useful method for synthesis of polycyclic ring systems. The generation of o-quinodimethane intermediates on the basis of thermal ring opening of benzocyclobutene, cheletropic elimination of 1, 3-dihydrobenzothiophene dioxide and 1, 4-elimination of o- (trimethylsilylmethyl) benzyltrimethylammonium halide, which have been conveniently utilized for the syntheses of a variety of polycycles, is described, focusing on preparations of the precursors for the generation of α-substituted o-quinodimethanes and their cyclizations to steroidal frameworks.
Organosilicon chemicals have been widely applied to the various industries. In this paper, the articles dealing with preparation of silanes and siloxanes in view of silicone industry, and application of silylating agents and silane coupling agents are reviewed (23 ref.).
Various organic groups have been introduced into silicone polymer in order to broaden its application. Amino, epoxy, carboxy, mercapto and alcohol groups in polysiloxane provide reactivity to ambient materials and additional function. Polyether, fluoroalkyl, alkyl, aralkyl, ester and alkoxy groups in polysiloxane provide new valuable properties. Preparation methods and charateristic applications of those organo-modified silicone fluids are reviewed.
Through many years, silicon has been considered to be biologically inactive. However, the developement in the field of organosilicon compounds has revealed that silicon is an essential element in the metabolic system. The present brief review is concentrated on the following items : a) A short survey of silicon compounds concerning life and its environment. b) A survey on a specified field of bioactive silicon compounds which have unique structures. c) A survey on a selected area of bioactive organosilicon compounds having analogous structures to bioactive parent carbon compounds.