Enamine Chemistry, Part XXI. N‐and/or C‐substitution (alkylation, acylation) of ethyl 3‐amino‐2‐butenoate. the preparation of 2‐substituted 4‐methyl‐1,3‐thiazine‐6‐thiones

Abstract Alkylation of ethyl 3‐amino‐2‐butenoate, 1, with methyl iodide, ethyl iodide, and benzyl bromide gave both C‐ and N‐alkylated products (contrary to earlier findings) the ratio of which was determined by GLC. Methylation of 1 was studied under different conditions (solvent, reaction time, and temperature). Also the sodium salt of 1 was reacted with methyl iodide and gave both C‐ and N‐methylated products. Compound 1 reacted with acyl chlorides RCOC1 (RCH 3 (a), CH(CH 3 ) (b), C(CH 3 ) 3 (c), C 6 H 6 (d), ClCH 2 (e)) giving both N‐acylated products 6 (Z) and 7 (E), and C‐acylated products 8 and 8'. Compounds 6 and/or 7 reacted with 2, 4‐bis (4‐methoxyphenyl)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide, 5, giving N‐thioacylated ethyl 3‐amino‐2‐butenoate, 9, and 2‐substituted 1,3‐thiazine‐6‐thiones, 11 (main product). A similar reaction of 8a with 5 gave ethyl 3‐amino‐2‐thioacetyl‐2‐butenoate, 13. The 13 C NMR data for the compounds 6, 7, 8, 11, 13, and to some extent 9 are presented.