The chemistry of small ring compounds. Part 36 CIDNP effects during the oxidation of substituted cyclopropanone methyl hemiacetals by di‐<i>tert</i>‐butyl diperoxyoxalate

Abstract

Abstract The reaction of tetramethylcyclopropanone methyl hemiacetal (2) and phenylcyclopropanone methyl hemiacetal (7) with di‐ tert ‐butyl diperoxyoxalate (TBPO) has been studied in connection with observed CIDNP effects. Oxidation of these hemiacetals by tert ‐butoxyl radicals (generated from TBPO) gives rise to the ring‐opened radical Me 2 • CCMe 2 COOMe (3) and C 6 H 5 • CHCH 2 COOMe (8) respectively. The existence of radical 3 is clearly demonstrated in benzene solution by the observed A/E multiplet effect for the disproportionation products HCMe 2 CMe 2 COOMe and H 2 CCMeCMe 2 COOMe, formed from two radicals 3 in a radical pair. In CDCl 3 solution, however, emissions are found for the unsaturated ester, CHCl 3 and CHDCl 2 , and an A/E signal for the saturated ester. The chlorinated products are formed from the • CCl 3 and • CDCl 2 radicals and a hydrogen donor. The benzylic radical 8 gives rise to an A/E multiplet effect (in benzene) for the combination product dimethyl 3,4‐diphenyladipate (9) and the disproportionation product methyl cinnamate (11).