Iron-catalyzed alkyne–carbonyl metathesis for the synthesis of 6,7-dihydro-5H-dibenzo[c,e]azonines

Abstract

The synthesis of nine-membered rings via alkyne–carbonyl metathesis is reported. The alkyne and acetal units contained in a biaryl substrate undergo the intramolecular alkyne–carbonyl metathesis reaction under FeCl₃-catalysis to furnish the unexplored 6,7-dihydro-5H-dibenzo[c,e]azonines. The method provides an alternative to existing routes to nine-membered rings with cheap, non-toxic iron catalysts and milder conditions.