The propargyltitanium reagents derived from 1-alkylpropyne condensed with aldehydes to give α-allenyl alcohol regioselectively, while the allenyltitanium reagents generated from 1-alky1-1-butyne derivatives gave threo-β-acetylenic alcohols with high regio- and stereoselectivities. The course of the reaction was determined by the substitution pattern of starting alkynes. The similar reactions of metallated
Boron reagents derived from trialkylsilylacetonitrites are effective for the synthesis of Z-α,β-unsaturated nitriles. Z-Terminal enyne units are synthesized from the titanium reagent from 1,3-bis-(trimethylsilyl)propyne and aldehydes.