Rhodium(I)/cationic 2,2′-bipyridyl-catalyzed [2+2+2] cycloaddition of α,ω-diynes with alkynes in water under air

A simply performed procedure for the (Rh(cod)Cl-2/cationic 2,2'-bipyridyl system-catalyzed [2+2+2] cycloaddition of alpha,omega-diynes with terminal and internal allcynes was achieved in water under air at 60 degrees C. The reaction proceeded smoothly with 1 equiv alpha,omega-diynes and 3 equiv alkynes in the presence of 20 mol % KOH for 1 h or 9 h, resulting in the formation of tri- and tetra-substituted benzene derivatives in moderate to high yields. After separation of the organic products by extraction, the residual aqueous solution could be reused for further reactions until complete degradation of its catalytic activity. (C) 2010 Elsevier Ltd. All rights reserved.