Vinylsilicon compound

Keywords cross-metathesis, silylative coupling, tmn.s-silylation, ruthenium catalysts, vinylsilicon compound... 

Silanes such as SiHCl3, CH3SiHCl2, C6H5SiHCl2, (CH3)(C6H5)SiHCl, and (C6H5)2SiHCl also add, at 160-400°, to olefins such as propene, 1- and 2-butene, hexene, and cyclohexene.330 Vinylsilicon compounds add such types of silane in the same way at about 300°, e.g.,331... 

Silanes can also be added to acetylenes, alkylacetylenes, acetylenic alcohols and their derivatives, etc., under conditions very similar to those effective with olefins, i.e.9 at high temperatures,367 with catalysis by peroxides,339,368 or in the presence of platinum361,369 or hydrogen hexachloroplatinate 370 palladium has proved a particularly effective catalyst for this reaction with acetylenes.371 The corresponding vinylsilicon compounds are formed, e.g. ... 

In the past decade two new catalytic reactions occurring between the same parent substances have been developed, namely silylative coupUng (trans-silylation) (Eq. 1) and cross-metathesis of alkenes (Eq. 2) with vinylsilicon compounds. 

Hetero-coupling polycondenastion of di- and tri-vinylsilicon compounds with organic dienes has permitted the synthesis of dendrimeric poly(silylene-arylene-vinylenes). 

Very recent reports on the activity of well-defined and functional group tolerant molybdenum and ruthenium-carbenes in the cross-metathesis of particularly alkoxy-and siloxy-substituted vinylsilicon compounds with a variety of olefins, indicate that this process is a very prospective route for synthesis of silicon-containing organic reagents under mild conditions. 

Although a lot of data have been reported on such competitive reactions, the number of examples of selective dehydrogenative silylation remains limited. Over the past two decades, the research efforts have been focused on the search for new selective catalysts of dehydrogenative silylation ensuring efficient generation of vinylsilanes and other vinylsilicon compounds as well as on mechanistic implications of transition metal complexes as real intermediates of these complicated processes. Dehydrogenative silylation has become a useful method for synthesis... 

A few other miscellaneous reactions may be noted. Vinylsilicon-metal compounds in entries 4 and 30 undergo addition of HBr in an anti-Markownikoff sense to give 2-bromoethyl derivatives in some other related systems, HBr induces cleavage (see Section III,B,2). Also, the phenyl group in a phenyl-silicon-metal compound can undergo hexahapto interaction with a Cr(CO)3 group (entry 39). 

Summary Two catalytic reactions, i.e. silylative coupling (mms-silylation) (SC) catalyzed by complexes containing or generating Ru-H and/or Ru-Si bonds (I, II, V, VI) and cross-metathesis (CM) catalyzed by mthenium-carbene (i.e. 1st and 2nd generation mthenium Grubbs catalyst (ID, IV)) of vinyl and allyl-substituted hetero(N,S,B)organic compounds with conunercially available vinyltrisubstituted silanes, siloxanes, and silsesquioxane have been overviewed. They provide a universal route toward the synthesis of well-defined molecular compounds with vinylsilicon functionality. 

In the last 15 years we have developed two new catalytic reactions between the same parent substances, i.e. silylative coupling (SC) (also called tmns-silylation or silyl groiq> transfer) and cross-metathesis (CM) of alkenes, which have provided an universal route for the synthesis of well-defined molecular compounds with vinylsilicon functionality. While the cross-metathesis is catalyzed by well-defined Ru and Mo carbenes, the silylative coupling is catalyzed by complexes initialing or generating M-H or M-Si bonds (where M = Ru, Rh, Ir). For recent reviews see Refs. [4-6],... 

Mechanistic implications of a general cross-metathesis of vinylsilicon with allyl-substituted heteroorganic compounds have been studied in detail for the reaction with allyl alkyl ethers [13]. The detailed NMR study of the stoichiometric reaction of Grubbs catalyst with allyl-n-butyl ether has provided information on individual steps of the catalytic cycle. A general mechanism of the cross-metathesis of vinyltri(alkoxy, siloxy)silanes (as well as octavinylsilsesquioxane) with 3-heteroatom-containing 1-alkenes in the presence of ruthenium carbene is shown in Scheme 5. 

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