Stereoselective formation of (2-thenyl)-substituted alkenes from 2-chloromethylthiophene and lithium trialkylalkynylborates

The reactions of 2-chloromethylthiophene (an analog of a benzyl halide) with lithium trialkylalkynylborates gave, after protonation, E-alkenes with a (2-thenyl) substituent in good yields, and the reaction stereo-selectivity was different from that of the reaction of benzyl bromide with an alkynylborate.