Cascade reaction including a formal [5 + 2] cycloaddition by use of alkyne-Co2(CO)6 complex

Abstract A new cascade reaction including formal [5 + 2] cycloaddition was developed. Treatment of homocinnamyl alcohol and Co 2 (CO) 6 -complexed arylpropynal with BF 3 ·OEt 2 resulted in the generation of hydrobenzocycloheptafuran having an alkyne-Co 2 (CO) 6 complex. The reaction consists of 5-membered ring selective Prins cyclization and subsequent Friedel-Crafts cyclization. The cascade reaction was applied to a further multi-step cascade cyclization, which resulted in the formation of more complex polycyclic hydrofurans.