The reaction of 8-chloro-3,4,5,6-tetrahydro-2H-1,6-benzothiazocine (I) with chloroacetonitrile (II) by means of Na2CO3 at 90 C gives 8-chloro-6-cyanomethyl-3,4,5,6-tetrahydro-2H-1,6-benzothiazocine (III), which is cyclized with N-isopropylethylenediamine (IV) by heating at 110 C with some CS2