Metal-Catalyzed Rearrangement of Homoallylic Ethers to Silylmethyl Allylic Silanes in the Presence of a Di-tert-butylsilylene Source

Abstract

[reaction: see text] In examining the scope of the di-tert-butylsilylene transfer to gem-disubstituted alkenes to form silacyclopropanes, we discovered an unprecedented reaction of homoallylic ethers. When silylene transfer was performed at room temperature or above, two di-tert-butylsilylene units were incorporated into the molecule, and complete rearrangement of the carbon backbone occurred. This report describes the scope of this unique reaction as well as the mechanistic studies conducted that led to a proposed mechanism.

Silver‐Catalyzed Silylene Transfer

“…85 No crossover was observed in the reaction of 87 and 88. Further, incorporation of deuterium into the silane and a position revealed that reorganization of the substrate had occurred.…”

“…85 At reduced temperatures, the reaction of homoallylic ethers with cyclohexene silacyclopropane 58 produced the expected silacyclopropane (Scheme 7.9, cf. 63g and 63h).…”

“…From these observations, Woerpel and Cleary proposed a mechanism to account for allylic silane formation (Scheme 7.23). 85 Silacyclopropane 94 is formed from cyclohexene silacyclopropane 58 through silylene transfer. Coordination of the Lewis basic benzyl ether to the electrophilic silicon atom [86][87][88] generates pentacoordinate siliconate 95 and increases the nucleophilicity of the apical Si--C bond.…”

On the ozonolysis of unsaturated tosylhydrazones as a direct approach to diazocarbonyl compounds

“…A 1:1 mixture of hydrazone 13 and benzylated isoprenol 14 10 (the latter to mimic the alkene present in 1) in CH2Cl2 underwent controlled ozonolysis at -78 °C in the presence of Sudan red 7B as an end-point indicator. 11 Ozonolysis was halted as soon as the colour of the reaction mixture changed from red to light pink.…”

Silylene-Mediated Ring Contraction of Homoallylic Ethers To Form Allylic Silanes

“…As part of our investigations into silylene transfer reactions to homoallylic ethers,14 we examined the reaction of (—)-isopulegol derivative 1 under the optimized reaction conditions. Subjection of benzyl ether 1 to cyclohexene silacyclopropane 2 and AgO 2 CCF 3 did not provide the expected silylmethyl allylic silane product.…”