REGIOSELECTIVE SYNTHESIS OF PIPERIDINONES BY METAL-CATALYZED RING EXPANSION CARBONYLATION REACTIONS - REMARKABLE COBALT AND OR RUTHENIUM CARBONYL CATALYZED REARRANGEMENT AND CYCLIZATION REACTIONS

Carbonylation of pyrrolidines, catalyzed by cobalt carbonyl, results in the formation of piperidinones. The reaction is regiospecific in most cases, and the yield of product is increased when ruthenium carbonyl is present as a second catalyst. The dual catalytic system [Co2(CO)8/Ru3(CO)12] is useful for the novel rearrangement of heterocyclic nitrogen ketones [(CH2)nCH2COR, n = 4-7] to lactams in 72-93% yields. An unusual metal catalyzed cyclization reaction of 2,6-dimethylpiperidinyl ketones afforded 5,6,7,8-tetrahydroindolizines in 86-94% yields.