Rhodium-catalyzed [2+2+2] cycloaddition of oximes and diynes to give pyridines.

Oximes and diynes undergo efficient cycloaddition in the presence of a catalytic amount of a cationic rhodium(I)/dppf complex (see scheme). Spontaneous dehydration of the initially formed cycloadducts leads to the formation of a variety of substituted pyridines in moderate to good yields. The transformation could also be achieved in a one-pot procedure using aldehydes.