TIN-COPPER TRANSMETALATION - CROSS-COUPLING OF ALPHA-HETEROATOM-SUBSTITUTED ALKYLTRIBUTYLSTANNANES WITH ORGANOHALIDES

Copper(I), in the absence of other transition metals, catalyzes the cr oss-coupling of (alpha-(acyloxy)benzyl)-tributylstannanes with allylic bromides in THF in fair to good yields and with aryl/vinyl halides le ss efficiently or not at all. Simple (alpha-(acyloxy)alkyl)tributylsta nnanes react sluggishly even with allyl bromide. However, proximal thi osubstituents on either reaction partner dramatically enhance yields, reaction rates, and the variety of suitable educts. (alpha-Phthalimido ylalkyl)tributylstannanes afford protected a-amino thio esters. In con trast with the Stille reaction, copper-mediated cross-couplings of alp ha-heteroatom-substituted alkyltributylstannanes proceed with complete retention of configuration via a coordinatively stabilized organocopp er intermediate that can be intercepted in good yield by 1,4-conjugate addition to 2-cyclohexen-1-one.