Silacyclobutyl ether

The silicon centers in silyl enol ethers and allylsilanes gain Lewis acidity when Si is incorporated into small cyclic structures. A representative example is enol silacyclobutyl ethers, which react with aldehydes at ambient temperatures possibly through a six-membered transition state (Scheme 3-122). Crotylbis(catechol)silicates react with aldehydes smoothly at the reflux temperature of THF also through six-membered transition states involving hexacoordinate silicates (Scheme 3-123). ... 

Scheme 3-122. Reaction of silacyclobutyl ethers with aldehydes.

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