Gold‐catalyzed [4+3]‐Annulations of Benzopyriliums with Vinyldiazo Carbonyls to Form Bicyclic Heptatriene Rings with Skeletal Rearrangement

We report gold catalyzed [4+3]‐annulations between benzopyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl carbonyls, yielding 7 H ‐benzo[7]annulene products efficiently. Notably, the carbon skeletons of resulting 7 H ‐benzo[7]annulenes are structurally rearranged, accompanied by migrations of their alkyl and ketone motifs. Apart from applicable substrates over a wide scope, these annulatios are applicable to pyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl esters to increase their reaction significance. We postulate a mechanism involving an initial [4+2]‐cycloaddition between benzopyriliums and 3‐alkyl‐2‐diazo‐3‐vinyl carbonyl species, followed by formation of gold carbenes to induce a ring expansion and group migrations. magnified image