REGIOSELECTIVE AND STEREOSELECTIVE RING OPENINGS OF UNSYMMETRICAL OXATRICYCLO ADDUCTS

S(N)2' ring-opening reactions of a number of substituted 11-oxatricycl o[6.2.1.0(1,6)]undec-9-en-5-ones prepared via the intramolecular Diels -Alder reaction employing a furan diene (IMDAF) are reported. Primary, secondary, and tertiary organolithium reagents were capable of effect ing the ring-opening reaction, while methyllithium required activation before any ring opening was observed. Hydride reagents, organocuprate s, and Grignard reagents were generally ineffective. The ring-opening reaction was highly regio- and stereoselective for attack at C-9 syn t o the bridging oxygen atom provided that C-8 was not substituted. A hi ghly stereoselective nucleophilic addition to the carbonyl group anti to the bridging oxygen was also observed. The high selectivity appears to be due to a combination of steric and electronic effects.