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Updated: Aug 29, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Regiocontrol in the oxidative radical fragmentation of benzilidene acetals and its mechanistic implications
James McNulty1, Jeff Wilson, Amanda C Rochon
1Department of Chemistry, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1. jmcnult@mcmaster.ca
Abstract:
The NBS-mediated oxidative fragmentation of benzilidene acetals has been investigated with mechanistic probes 12, 14, and 18 designed to discriminate between the possible competitive pathways. Results indicate that fragmentation of the initial benzylic radical 19 does not occur spontaneously but that oxidation proceeds rapidly to give the benzyl bromide 20, which then fragments via a polar pathway. Reversed regiospecificity in the fragmentation is demonstrated for the first time through the incorporation of an allylic alcohol into the benzilidene acetal.
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