The reaction of 2‐mercaptobenzothiazole, 2‐mercaptobenzoxazole or 5‐chloro‐2‐mercaptobenzothiazole with either acrylonitrile or acrylamide under basic conditions afforded the N‐cyanoethylated products 1, 2 and 3 or the N‐amidoethylated products 4, 5 and 6, respectively. The reaction of the sodium salts of the same thiazolethiols with 3‐chloropropionitrile furnished a mixture containing the N‐cyanoethylated products 1, 2 and 3 and the unknown S‐cyanoethylated products 7, 8 and 9, respectively. Whereas, substituting 3‐chloropropionamide for 3‐ chloropropionitrile in the same reaction gave only the S‐substituted products 10, 11, and 12, respectively. The treatment of 10, 11 or 12 with phosphorus oxychloride or thionyl chloride in DMF afforded 7, 8 and 9 in excellent yields. Possible mechanisms and supporting nmr data are discussed.