SYNTHESIS OF MACROCYCLIC KETOESTERS BY AN N-RADICAL CARBONYLATION(1 STRATEGY BASED ON FREE)

The synthesis of 10-17 membered 4-oxolactones 2 from alkyl iodides 1 h aving an acryloxy moiety at the termini, carbon monoxide, and TTMSS (o r tin hydride) was achieved under free radical reaction conditions. Th e allyltin mediated reaction of 1 also proceeded successfully to furni sh 2-allyl-substituted 4-oxolactones 3 in moderate to good yields. In this n + 1 type macrocyclization, high dilution conditions ([1] = 0.00 5-0.01 M) are beneficial for both the intermolecular trapping of CO an d the intramolecular acyl radical addition to the C-C double bond. (C) 1997 Elsevier Science Ltd.