FREE-RADICAL RING EXPANSION BY ONE-CARBON ATOM BY DECOMPOSITION OF THE THIOHYDROXAMIC ESTERS OF (1-ALKOXYCARBONYL-2-OXOCYCLOALKYL)ACETIC ACIDS

A free-radical ring expansion by one carbon atom has been achieved by thermal decomposition of thiohydroxamic esters of (1-alkoxycarbonyl-2- oxocycloalkyl)acetic acids, 8. Thus, by decomposition of thiohydroxami c esters 8a-f in boiling toluene, ethyl 3-oxocycloalkenecarboxylates 9 a-f are obtained as principal ring-enlarged products in 27-58% yield; accompanied by ethyl l-2-thiazolylthio)-3-oxocycloalkane-1-carboxylate s 10c,d (24% yield) with the ring expanded by one carbon atom. Unrearr anged ethyl azolylthiomethyl)-2-oxocycloalkane-1-carboxylates) 11a-f a re formed as side products (8-17% yield). Ring expansion involves the following sequence of reactions: 3-exo-cyclization (to C=O group), cle avage of the cyclopropane ring, intermolecular addition to the thione group of thiohydroxamic esters and elimination reaction.