PELLETIERINE CONDENSATION - MECHANISTIC STUDIES

Evidence is presented to show that the pelletierine condensation proceeds via a Claisen-Schmidt condensation to the enone 8, which cyclizes to the 4-aryl-2-quinolizidinones by an intramolecular Michael-type addition. In aprotic solvents, 8 afforded the less stable cis-quinolizidinone (3) with relatively high selectivity. The implications of this finding for the mechanism of the isomerization of the cis-to the trans-quinolizidinones are discussed. In protic solvents the isomerization occurred without added base. The pelletierine condensation was also found to proceed in low yield under acidic conditions. An unusual carbonyl-assisted hydrolysis of a trifluoroacetamide was observed. An efficient procedure for the large-scale preparation of pelletierine is described in the Experimental Section. © 1979, American Chemical Society. All rights reserved.