Decomposition of 2-(1-hydroxybenzyl)thiamin. Ruling out stepwise cationic fragmentation.
[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.
Moore
I F
IF
Lash Miller Laboratories, Department of Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 3H6.
Kluger
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D001386:Azides / Q000737:chemistry; D002412:Cations; D007202:Indicators and Reagents; D011522:Protons; D011743:Pyrimidines / Q000737:chemistry; D013831:Thiamine / Q000031:analogs & derivatives* / Q000737:chemistry*
D001386:Azides; D002412:Cations; D007202:Indicators and Reagents; D011522:Protons; D011743:Pyrimidines; D013831:Thiamine