Fragmentation of the Breslow intermediate is a radical process.

by May, Alexa; McIntosh, Matt

Thiaminediphosphate (TDP) is a cofactor in many essential processes such as in the pentose phosphate pathway, citric acid cycle, and amino acid catabolism. In 1970 Oka and coworkers discovered a fragmentation of thiamine while looking into thiamine and related analogs as catalysts in the benzoin condensation. Several years later Kluger et al obsd. a similar fragmentation, which he designated the Oka fragmentation, in aq. soln. and proposed a polar pathway for the process. Recently, we reported analogous fragmentations of Breslow-type intermediates. Trapping expts. and computational anal. supported a radical, rather than polar pathway. Bielecki and Kluger have challenged these results. Addnl. evidence for a radical pathway and further studies into the fragmentation will be discussed.