Diastereospecific Gold(I)‐Catalyzed Cyclization Cascade for the Controlled Preparation of N‐ and N,O‐heterocycles

The reaction of oxime‐tethered 1,6‐enynes with a cationic gold(I) catalyst demonstrates a great potential for the synthesis of a range of heterocycles in a diastereospecific fashion. The control of the configuration of the oxime and the alkene of the enyne moiety is the key to obtain selectively dihydro‐1,2‐oxazines, isoxazoles or dihydropyrrole‐N‐oxides as single diastereoisomers. As supported by DFT calculations, these cascade reactions proceed stepwise, by the intramolecular addition of the O or N atom of the oxime onto cyclopropyl gold(I) carbene intermediates. In this study, we have also observed a rare [3,3]‐sigmatropic rearrangement of nitrones.