Ring Contraction of 1,2,4,5,7,8-Hexaoxa-3-silonanes by Selective Reduction of COOSi Fragments. Synthesis of New Silicon-Containing Rings, 1,3,5,6-Tetraoxa-2-silepanes

The reducing agents Ph3P, (C8H17)3P, or NH2C(S)NH2 promote the ring contraction of nine-membered triperoxides, viz., 1,2,4,5,7,8-hexaoxa-3-silonanes, giving rise to seven-membered rings belonging to the previously unknown class of monoperoxides, viz., 1,3,5,6-tetraoxa-2-silepanes, in yields from 67% to 91%. Therefore, the selective reduction of the SiOOC fragments to SiOC in molecules containing simultaneously the COOC fragment was performed for the first time.