Gold-Catalyzed Formal [3 + 3] and [4 + 2] Cycloaddition Reactions of Nitrosobenzenes with Alkenylgold Carbenoids

We report two new formal cycloaddition reactions between
nitrosobenzenes
and alkenylgold carbenoids. We obtained quinoline oxides 3 in satisfactory yields from the gold-catalyzed [3 + 3]-cycloadditions
between nitrosobenzenes and alkenyldiazo esters 1. For
propargyl esters 5, its resulting gold carbenes react
with nitrosobenzene to give alkenylimine 8, followed
by a [4 + 2]-cycloaddition with nitrosobenzene.