Boron Compounds. XLIV The Influence of Silicon on the Formation of (Z/E)-Tetrasubstituted Ethylenes via 1-Alkynylborates2

摘要

Sodium triethyl- (I) and triphenyl-trimethylsilylethynylborate (II), when treated with electrophilic reagents give (Z/E)-mixtures of tetrasubstituted alkenes III and IV. The influence of the trimethylsilyl group, incorporated in the borates I and II, on the stereoselectivity of the reaction was studied with the aid of1H and11B nmr. A novel rearrangement of bis-trimethylsilylalkenes IIId and IVd was also investigated.