Novel Use of Organotin Compounds by Using Higher Coordinating Method.

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This study deals with novel synthetic use of organotin enolates and organotin hydrides, in which complexation of tin compounds with Lewis bases played an important role.1. The reaction of tin enolates with alpha-haloketones. Tin enolates have been reported to react with alpha-haloketones at the carbonyl group to afford halohydrins or oxirane ring. In contrast, We have found the addition of coordinating compounds such as phosphine oxides to this reaction system afforded complete reversed chemoselectivity. Namely, the coupling reaction of tin enolates with halide group of alpha-haloketones took place. The formation of higher coordinated tin enolates played an important role for this unusual reactivity. This higher order species were detected by NMR spectra. Moreover, in addition of chemoselectivity, recent study revealed that control of stereoselectivity was established by using presented higher coordinated tin species.2. Reduction of alpha-alkoxyketones with higher coordinated tin hydrides. In contrast to the conventional use using radical method, tin hydrides was revealed to employ efficient hydride donors by complexation with Lewis bases. Namely, this higher coordinating method afforded syn-alkoxy alcohols stereoselectively in the reduction of alpha-alkoxyketones. These results could be explained in terms of Felkin model. Moreover, recently, we have also recognized the stereoselective reaction in the reaction of alpha,beta-Epoxyketones.