Intramolecular reactions of o-alkoxy- and o-alkylthio-benzyl radicals

Abstract

We report new gas-phase reactions of o-substituted benzyl radicals produced by flash vacuum pyrolysis of 2,3-dihydro-1,3,2-benzoxazaphosph(V)oles (4)–(6), dibenzyl sulphone (8), and dibenzyl oxalates (9)–(11). Both o-ethoxy- and o-methoxy-benzyl radicals rearrange to o-tolualdehyde via intramolecular hydrogen transfer, as shown by experiments using 2-[²H₃]methoxybenzyl radicals. o-Methylthiobenzyl radicals do not give the corresponding thioaldehyde, but produce a mixture of benzocyclobutene and isomeric dihydrobenzothiophens by novel rearrangement reactions. o-Ethylthio- and o-propylthio-benzyl radicals give o-methylstyrene and o-propenyltoluenes respectively as major products.