Ruthenium-catalyzed [2+2] cycloadditions between C1-substituted 7-oxanorbornadienes and alkynes

Ruthenium-catalyzed [2+2] cycloadditions between Cl-substituted 7-oxanorbornadienes and alkynes were investigated. Most of the cycloadditions occurred smoothly at 65 degrees C, giving the cyclobutene cycloadducts in moderate to good yields. The Cl substituent showed si rong effect on the regioselectivity (up to 110:1) of the cycloadditions. (c) 2006 Elsevier Ltd. All rights reserved.