Copper-catalyzed [4 + 1] cycloadditions of alpha,beta-acetylenic ketones with diazoacetates to form trisubstituted furans.

Copper-catalyzed [4 + 1] cycloaddition reaction of alpha,beta-acetylenic ketones with alpha-diazo esters offers an efficient, direct route to highly substituted furans. The reaction conditions and the scope of the process are examined, and a possible mechanism is proposed.