Abstract
The addition of dialkylzincs or diphenylzinc to substituted phenylacetylenes in the presence of catalytic amounts of Ni(acac) 2 in THF : NMP mixtures produces syn-carbozincation products with good to excellent regio- and stereoselectivity. After quenching with an electrophile (iodine, acyl chloride, allyl bromide) tetrasubstituted olefines are obtained in good to satisfactory yields. An intramolecular version of the reaction is possible using a terminal triple bond bearing an iodine at a remote position. More substituted iodo-alkynes furnish only reductive elimination products. An application to a stereoselective synthesis of (Z)-tamoxifen (Z : E>99 : 1) has been developed.
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