Ruthenium-catalyzed [2+2+2] cycloaddition of three different alkynes

A chemoselective, [2 + 2 + 2] cycloaddition of an internal alkyne, a terminal alkyne and dimethyl acetylenedicarboxylate was efficiently catalyzed by Cp*RuCl(cod) to give trisubstituted o-phthalates in good yield. lt is critical to control the molar ratio of the three substrates to achieve high chemoselectivity, and regioselectivity of the products is sensitively influenced by the bulkiness of substituents on the internal alkyne. (c) 2005 Elsevier B.V. All rights reserved.