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Decomposition of 2-(1-hydroxybenzyl)thiamin. Ruling out stepwise cationic fragmentation
1Lash Miller Laboratories, Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6.
Organic Letters
|July 13, 2000
Abstract:
[reaction: see text] The rapid fragmentation of 2-(1-hydroxybenzyl)thiamin (1) is initiated by transfer of a proton from C2alpha to give an enamine. The subsequent irreversible process can be written as a concerted (or stepwise) rearrangement involving migration of the hydroxyl hydrogen to the methylene bridge. An attractive alternative is internal addition of C2alpha to the pyrimidine, generating a carbocation. However, addition of azide to the reaction solution, which could trap the carbocation, has no effect on the rate or products of reaction.