Total Synthesis of (±)-Tazettine

The total synthesis of (±)-tazettine ( 1 ) has been achieved in 16 steps from commercially available piperonyl alcohol in 11% overall yield. The crucial quaternary center was assembled by a novel [4+1] cycloaddition between dimethoxycarbene and β-aryl vinyl isocyanate ( 4 ). Samarium diiodide conditions were employed to reduce the enamide unsaturation in the [2]benzopyrano[3,4- c ]hydroindole intermediate 19 to compound 20 exhibiting a cis -AB ring fusion.