摘要:
Z-Enynes, RCH=CHC=CH (R= phenyl, 2-furyl, 2- and 3-thienyl and 3-pyridyl) can be obtained in approximately 40% overall yields and with a stereoselectivity of > 95% by Pd/Cu-catalyzed cross-coupling of the readily available enyne sulfide HC=CCH=CHSC2H5 with RBr and RI, reduction of the products with activated zinc powder in ethanol and elimination of ethanethiol from the reduction products RCH=CHCH=CHSC2H5 with an excess of sodamide in liquid ammonia. In the case of the 2-pyridyl-substituted substrate the E-enyne HC=CCH=CH-2-pyridyl is isolated.