Alkenes, reactions 3-Alkoxysilanes

When phenyl(trimethylsilyl)diazomethane (20) is pyrolyzed in the gas phase, typical reactions of carbene 21 can be observed (see Section III.E.4). However, copyrolysis with alcohols or carbonyl compounds generates again products which are derived from silene 2239,40 (equation 6). Thus, alkoxysilanes 23 are obtained in the presence of alcohols and alkenes 24 in the presence of an aldehyde or a ketone. 2,3-Dimethylbuta-l,3-diene traps both the carbene (see Section ni.E.4) and the silene. 

Over the past ten years, absolute rate data have been reported on the kinetics of several bimolecular silene reactions in solution, including both head-to-tail and head-to-head dimerization the [l,2]-addition reactions of nucleophilic reagents such as water, aliphatic alcohols, alkoxysilanes, carboxylic acids and amines and the ene-addition, [2 + 2]-cycloaddition and/or [4 + 2]-cycloaddition of ketones, aldehydes, esters, alkenes, dienes and oxygen. The normal outcomes of these reactions are summarized in Scheme 1. 

Tris(thioalkyl)silanes may be prepared by reaction between ClsSiH and thiols in a manner similar to the preparation of alkoxysilanes and are useful reagents for radical reductions of alkyl halides or alkenes in organic chemistry (Scheme... 

Hoye and Promo examined the effect of ring size and alkene substitution on /Z-selectivity and rate of reaction (Table 8.2) [15]. This study also employed the diphenylsilane as the linker for the construction of symmetrical his-alkoxysilanes. 

Interchanging the order of the CM and TST-RCM reactions allows for the preferential functionalization of the less hindered and more reactive Type I alkene and thus permits the formation of the seven-membered silaketal without competitive RCM. A critical feature for the success of this strategy is that the formation of the cis-silaketal is preferred over the trans-derivative, which provides optimal rates of reaction [22]. Treatment of a mixture of the unsymmetrical bis-alkoxysilane 58 and butenolide 60 (1 4 ratio) with catalyst [Ru]-III provided the gigantecin skeleton 62 in 63% yield in a single step. Additionally, the formation of the homodimer of butenolide 60 is inconsequential since it can be recycled through... 

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