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Reaction of 3-aryl-5-methylisothiazoles (4) with aromatic nitriles afforded the adducts 3, 5-(2-amino-2-arylvinyl)-3-arylisothiazole derivatives, in the presence of LDA. By employing p-chlorobenzonitrile-15lV, the presence of ring transformation from one isothiazole (a form) to another isothiazole {ß form) was verified. By spectral analyses of 3 compared with 5-[2-(silylamino)-2-arylvinyl]-3-arylisothiazole (13-Z), 3 was concluded to have trans geometry (3-Z) with respect to two aromatic rings to arrange N-8••• linearly. The pure a isomers of 15N-labeled 3d (3d*-a-Z: Ar1 = Ar2 = p-ClC6H4), 3b (Ar1 = p-C1C6H4, Ar2 = p-MeC6H4), and 3e (Ar1 = p-ClC6H4, Ar2 = 3,5-Cl2C6H3) were synthesized by desilylation of 13b, 13d*, and 13e-Z and the equilibrium between a form and ß form has been shown to take place in neutral solutions. A

A new catalytic system using the combination RuCl2(DMSO)4/CH3CH2COONa/DMSO/carboxylic acid which enables selective dimerization of acrylonitrile to linear dimers without formation of propionitrile as a byproduct has been developed on the basis of a new working hypothesis of the desirable reaction mechanism involving protonolysis of a C−Ru bond in the intermediate.