(Z)-3-p-tolylsulfinylacrylonitriles as chiral dipolarophiles: Reactions with diazoalkanes

GRAPHICS The dipolarophilic reactivity of enantiopure (Z)-3-p-tolylsulfinylacrylonit riles (1) has been evaluated with diazoalkanes. 3-Cyanopyrazoles are obtain ed when R = H, but with R = alkyl (Bn, n-Bu, and t-Bu) only one cycloadduct (4 or 5) is formed in high yield under mild conditions, therefore evidenci ng a complete control of the regioselectivity and the endolexo and pi -faci al selectivities. These reactions are a new straightforward entry to the sy nthesis of pyrazolines and related structures and reveal the excellent dipo larophilic features of (Z)sulfinylacrylonitriles.