Au(I)‐Catalyzed Annulation of Benzofurazan N‐oxides with Ynamides: From Predicting the Chemo‐Selectivity to the Synthesis of 7‐Nitroindole Derivatives

Abstract

Summary of main observation and conclusionIt could be proposed that gold(I)‐catalyzed reactions of ynamides with benzofurazan N‐oxides might proceed through either O‐attack or N‐attack to afford α‐oxo or α‐imino Au(I)‐carbenoid intermediates. Computational studies were performed to predict that benzofurazan N‐oxides are ready to undergo the chemoselective N‐attack to the Au(I)‐activated ynamides to generate the α‐imino Au(I)‐carbenoid intermediate. Experimental studies were carried out to confirm the computational results and the 7‐nitroindole derivatives were synthesized in a concise and efficient manner. The unfavored O‐attack for benzofurazan N‐oxides, which is in contrast to nitrones and pyridine/quinoline N‐oxides, in the Au(I)‐catalyzed reactions with ynamides is rationalized.