Formation of macrocyclic lactones in the Paternò-Büchi dimerization reaction.

Furan-2-ylmethyl 2-oxoacetates 1a,b, in which the furan ring and the carbonyl moiety were embedded intramolecularly, were synthesized from commercially available furan-2-ylmethanol and their photochemical reaction (hν > 290 nm) was investigated. Twelve-membered macrocyclic lactones 2a,b with C(i) symmetry including two oxetane-rings, which are the Paternò-Büchi dimerization products, were isolated in ca. 20% yield.