Thomas Stüdemann

An Efficient Nickel‐Catalyzed Cross‐Coupling Between sp3 Carbon Centers

Since the pioneering work of Wurtz, cross-couplings between sp3 carbon centers have had the reputation of being difficult. In the presence of a catalytic amount of m-trifluoromethylstyrene, an efficient cross-coupling reaction takes place between polyfunctional primary alkyl iodides and diorganozinc compounds [Eq. (a)] to give a general catalytic cross-coupling between sp3 carbon centers. Piv=pivaloyl; Pent = pentyl; acac = acetalacetonate; NMP = N-methylpyrrolidone.

A Nickel-Catalyzed Carbozincation of Aryl-Substituted Alkynes

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.

Nickel catalyzed tellurium-zine exchange reactions. A new preparation of arylzinc reagents

Diaryltellurides 2 and diarylditellurides 3 undergo a smooth tellurium-zinc exchange reaction in the presence of catalytic amounts of Ni(acac)2 (5–10 mmol %) leading to arylzinc derivatives 1. The reaction can be extended to the preparation of alkylzinc compounds and allows a stereoselective cyclization to a 2,4-disubstituted tetrahydrofuran by a radical ring closure of an unsaturated telluride.