The regioselective ring-opening of ring-substituted cyclopropylcarbinyl radicals: variation of the substituent

Abstract

The cis- and trans-2-ethyl- and 2-t-butyl-cyclopropylcarbinyl radicals (A; M = H or Bu₃Sn; R = Et or Bu^t) were generated by the addition of tributyltin radicals to the appropriate ketone, or abstraction of hydrogen from the appropriate carbinols, and the intermediate radicals and the ultimate products were monitored by e.s.r. spectroscopy [graphic omitted] and by g.l.c. respectively. It is shown that the ethyl and t-butyl substituents exert the same directive effect as the methyl group in that whereas the cis-reactants undergo ring opening to give predominantly the secondary alkyl radicals (B) the trans-reactants give the thermodynamically less stable primary alkyl radicals (C).