Functionalised benzocyclo-octenones: synthesis and chemistry

Abstract

10,11-Dihydro-5-hydroxy-4-methoxycarbonylbenzo[5,6]cyclo-octa[1,2-c]furan-1,3-dione was selectively reduced and hydrolysed to 4,5-dihydrobenzo[5,6]cyclo-octa[1,2-c]furan-1,10(3H,11H)-dione whose structure was confirmed by X-ray analysis. Reduction and dehydration gave the lactone 10,11-dihydrobenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one which was identical with one of two isomers obtained when the anhydride 10,11-dihydrobenzo[5,6]cyclo-octa[1,2-c]furan-1,3, 5(4H)-trione was reduced and dehydrated. Products of bromination of 10,11-dihydrobenzo[5,6]cyclo-octa [1,2-c]furan-1,3,5(4H)-trione and its methyl enol ether were identified: the enol ether was converted into several imides which could not be cleanly reduced. 4,5-Dihydrobenzo[5,6]cyclo-octa[1,2-c]furan-1,10(3H,11H)-dione was converted into the following lactones: 4,5,10,11-tetrahydro-10-hydroxybenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one; 4,5-dihydrobenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one; 3a,4,5,10,11,11a-hexahydro-10-hydroxybenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one; 4,5,10,11-tetrahydro-10-hydroxybenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one; 3a,4,5,11a-tetrahydrobenzo[5,6]cyclo-octa[1,2-c]furan-1,10(3H,11H)dione; 3a,4,5,11a-tetrahydrobenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one. Reaction of appropriate lactones with benzylamine and benzylamine hydrochloride or with methylamine and hydrogen chloride gave lactams which were reduced to N-benzyl or N-methyl benzo[5,6]cyclo-octa[1,2-c]pyrrole derivatives. N-Benzyl analogues were debenzylated via carbamates. 4,5,10,11-Tetrahydro-10-hydroxybenzo[5,6]cyclo-octa[1,2-c]furan-1(3H)-one was arylated with anisole in the presence of acid to yield 4,5,10,11-tetrahydro-p-methoxyphenylbenzo[5,6]cyclo-octa[1,2-c]furan-1 (3H)-one.