Novel rearrangements and formation of 2,5-dihydro-1,2,5-oxoniastannaboratoles via methanolysis of zwitterionic η2-(alkyn-1-yl-borate)alkenyltin compounds

Wrackmeyer B.; Kehr G.; Willbold S.; Boese R.

Abstract

Organo-substituted 2,5-dihydro-1,2,5-oxoniastannaboratoles 3 were prepared by methanolysis of zwitterionic η2-(alkyn-1-ylborate)alkenyltin compounds 1. Analogously, the bis[η2-(alkyn-1-yl-borate)alkenyltin derivative 2 reacts with an excess of methanol to give a dimeric MeO-bridged 2,5-dihydro1,2,5-oxoniastannaboratole (10a)2. Various intermediates could be identified by NMR spectroscopy, and the molecular structure of (10a)2 was determined by X-ray analysis. The structures of several products of the methanolysis indicate that protolysis of an Sn-C= bond occurs first, followed by an MeO/alkenyl exchange reaction. ©1999 KluwerAcademic/Plenum Publishers.