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

Azaspiro[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. (Figure presented.).