Oxidative Grob Fragmentation of γ-Tributylstannyl Alcohols with a Combination of Iodosylbenzene, Dicyclohexylcarbodiimide, and Boron Trifluoride

Article abstract of DOI:10.1021/jo00281a026

Exposure of cyclic γ-stannyl alcohols, prepared from cyclic vinyl ketones, to a combination of iodosylbenzene, dicyclohexylcarbodiimide, and boron trifluoride-diethyl ether in dichlorometane undergoes an oxidative Grob fragmentation to give unsaturated carbonyl compounds.The dicyclohexylcarbodiimide in this reaction apparently activates iodosylbenzene and decreases Lewis acidity of boron trifluoride.The fact that the iodine(III)-mediated Grob fragmentation proceeds stereospecifically suggests the fragmentation is concerted.The fragmentation, combined with conjugate addition of (tributylstannyl)lithium and reduction or alkylation, offers an efficient procedure for the reductive and alkylative ring opening of cyclic vinyl ketones.Since cis-benzyl ether 36, after quenching of the reaction mixture with aqueous NH4Cl, afforded the chlorostannane 37, the reaction mechanism involving the formation of iodine(III) species 32 with two oxygen ligands at iodine proposed.