Synthesis of Azulen-1-yl Ketones via Oxidative Cleavage of C-C Multiple Bonds in N-Sulfonyl Enamides and 1-Alkynes under Air and Natural Sunlight.

A synthetic method to prepare azulen-1-yl ketones was developed via oxidative cleavage of the C-C double bond in the reaction of easily obtainable N-sulfonyl enamides with Cs2CO3 under air and natural sunlight and in the absence of a photosensitizer. Oxidative cleavage of C-C triple bonds was also demonstrated for the synthesis of azulen-1-yl ketones via a tandem Cu-catalyzed [3 + 2] cycloaddition, Rh-catalyzed arylation, photooxygenation, and ring-opening reaction in one pot under air and natural sunlight.