Electron spin resonance studies of radical addition to alkynes and intramolecular reactions of vinyl radicals

Abstract

E.s.r. spectra are described of radicals formed by the reactions of some alkynes both with hydroxyl and also with radicals formed from a variety of ethers in the presence of hydroxyl. Vinyl radicals, though not normally detected, are apparently involved, and evidence is presented for their intermolecular addition and intramolecular abstraction reactions. For example, the vinyl radical produced by addition of ·CHMeOEt to HO₂CCCCO₂H reacts to form the allyl radical ·CHMeC(CO₂H)CHCO₂H, evidently via a 1,5 carbon-to-carbon hydrogen shift and fragmentation. Other instances of ready 1,5-shifts (including an oxygen-to-carbon example) are described.