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

Abstract

AbstractThe 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 Me2 •CCMe2COOMe (3) and C6H5•CHCH2COOMe (8) respectively. The existence of radical 3 is clearly demonstrated in benzene solution by the observed A/E multiplet effect for the disproportionation products HCMe2CMe2COOMe and H2CCMeCMe2COOMe, formed from two radicals 3 in a radical pair. In CDCl3 solution, however, emissions are found for the unsaturated ester, CHCl3 and CHDCl2, and an A/E signal for the saturated ester. The chlorinated products are formed from the •CCl3 and •CDCl2 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).