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[reaction: see text] Highly enantiopure (R)-2-p-chlorophenyl-2-(1H-1,2,4-triazol-1-ylmethyl)hexanenitrile 1 (myclobutanil or systhane) was obtained in six synthetic steps from commercially available 1-hexyne (35% yield, 92% ee). The sulfinyl group controls the two key steps of the synthetic sequence, the highly stereoselective hydrocyanation of vinyl sulfoxides with Et(2)AlCN and the further introduction of the proper functionality into the molecule.

Results obtained in the reactions of Et 2 AlCN with exocyclic, endocyclic, and acyclic α-ptolylsulfinyl ketimines are reported. Good conversions and satisfactory stereochemical results are obtained exclusively from cyclic ketimines. Imine-enamine equilibrium accounts for the incomplete conversions and low reactivities observed for acyclic amines. Configurational assignments and mechanistic proposals are based on the conformational analysis of substrates and products.

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Terminal alkynes are easily transformed into enantiomerically enriched compounds containing tertiary and quaternary carbon atoms. Sulfinylation followed by reduction (or alkylation) and hydrocyanation of the resulting vinyl sulfoxides with Et2AlCN provides nitriles bearing the chiral center, which can in turn undergo reaction to form the desired products (see reaction scheme). Tol=4‐tolyl.