Molybdenum-mediated cyclocarbonylation of 1-ethynyl-2-allenylbenzenes to 1H-cyclopenta[a]inden-2-ones

Although 1-ethynyl-2-allenylbenzenes readily undergo Myers–Saito or Schmittel cyclization under mild conditions, cyclocarbonylation of these moieties to 1H-cyclopenta[a]inden-2-ones proceeds smoothly using suitable molybdenum carbonyl reagents, with Mo(CO)3(CH3CN)3 being the most efficient. The yields of desired bicyclic ketones were up to 87–93%.