Silylated cyclohexadiene with alkene

In general, radical hydrosilylation of alkenes cannot be conducted with tri-alkylsilanes, which is due to a rather strong Si—H bond in the latter. However, the hydrosilylation of carbon-carbon multiple bonds with modified silanes such as tris(trimethylsilyl)silane has been successfully used in radical hydrosilylation (16). The reversible addition of tris(trimethylsilyl)silyl [(TMSlsSi] radical to the C=C bonds is due to the ability of this radical to isomerize alkenes. The hydrosilylation of monosubstituted and gem-disubstituted olefins are efficient processes and have been shown to proceed with high regioselectivity for both electron-rich and electron-poor olefins (140). Walton and Studer presented the results of the radical hydrosilylation with silylated cyclohexadienes as radical initiators (141). The bisvinylic methylene group acts as the hydrogen donor in these reactions. H-transfer leads to a cyclohexadienyl radical (2) that subsequently rearranges to provide er -butyldimethylsilyl radical and arene (3) (see Scheme 20) (141). 

Dienes such as cyclohexadiene or cyclopentadiene react with trichlorosilane in the presence of 0.1 mol % of a palladium catalyst generated in situ by mixing 1 and a chiral phosphane (eq 96). The use of chiral MOP-phen (3-diphenylphosphino-3 -methoxy-4,4 -biphenanthryl) afforded the highest enantiomeric excess, as the silylated alkene was obtained in 99% yield and 80% ee. 

Phosphonyl and phosphinyl nitroso alkenes (607) reacted with cychc conjugated nucleophilic dienes such as cyclopentadiene or cyclohexadiene (608) and silyl-substituted cyclopentadiene (609) to afford [4+2]-hetero Diels-Alder-type 1,2-oxazines cycloadducts (610) and (612) The nitroso alkenes participated as dienophile components and the cyclic olefins acted as the 471-electron (diene) systems. Cycloadducts (611), derived from cyclopentadiene, underwent a new aza-Cope type [3,3]-sigmatropic rearrangement to give 1,2-oxazines (612) (Scheme 150). ... 

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