Access to 3‐(2‐Oxoalkyl)‐azaspiro[4.5]trienones via Acid‐Triggered Oxidative Cascade Reaction through Alkenyl Peroxide Radical Intermediate

International audienceAzaspiro[4.5]trienones bearing ketone side chains at the 3-position are prepared from N-alkyl-arylpropiolamides and ketones via oxidative 1,2-difunctionalization of alkynes. The cascade sequence starts with the generation of alkenyl peroxide intermediates, which are obtained by addition of tert-butyl hydroperoxide to ketones in presence of a catalytic amount of a strong acid. Then, the ketone radical adds to alkynes, followed by spirocyclization and dearomatization process. This method represents a new example of difunctionalization of alkynes with simultaneous formation of two carbon-carbon single bonds and one carbon-oxygen double bond in one step