Synthesis of 1,3‐Difunctionalized Cyclopentenes and 1,3,5‐Trifunctionalized Cyclohexanes by Silicon‐Induced Domino Reactions

A novel domino process based on a 1,4‐C⇄O shift of a silyl group ( 4 ⇄ 3 ) and a Michael‐induced ring‐closure reaction ( 3 ⇄ 2 ) is investigated. Specifically, attack of carbanions 5 on vinyloxiranes 6 usually occurs on the oxirane unit to give the desired silyl shift. When starting from vinyloxiranes 6a and 6b , however, the reaction stops at this stage to give silyl ethers 7 . Sulfur ( 6c ) or silicon activation ( 6d − f ) of the C=C unit is required to yield cyclopentenes 1a − d . Analogously, carbanion 5a and allyloxiranes 15 give cyclization products 19 − 22 , particularly if the ring‐closure step is supported by silicon substitution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)