Treatment of acetophenone with PhCH2Mn (CO) 5 in refluxing heptane provides (q2-2- acetylphenyl) tetra-carbonylmanganese in high yield. Conversion of the manganese complex to a reactive 16-electron species by oxidative decarboxylation with Me3N-0 in CH3CN, followed by reaction with an alkyne, directly yielded substituted 1-methyl-1H-inden- 1-01s in very good yields. The reaction is highly regioselective for terminal, electron-rich, ...