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Ambident reactivities of alkoxycarbonyl isothiocyanates (2) with heterocyclic amines were discussed from the concept of charge and frontier controlled interactions which is a qualitative interpretation of the hard and soft acids and bases (HSAB) principle. The calculated charge densities indicate hard nucleophiles have the tendency to attack on the carbonyl carbon atom and soft nucleophiles on the isothiocyanato moiety of 2. To clarify the difference in basic behavior of heterocyclic amines, correlations existing in the ionization data of pyridinium and thiazolium ions were analyzed using the dual substituent parameters of F (field) and R (resonance). It seems likely that the F effect results mostly from charge controlled interactions and the R effect from electron transfer interactions between the nearly degenerate overlapping orbitals. It was suggested that the magnitude of the F and R factors of the regression equations can be an indication of the charge and frontier controlled interactions between the two interacting molecules and the F effect may have an important role in determining the pathway of approach in the initial stage of the reactions.

Reactions of ethoxycarbonyl isothiocyanate (2a) with heterocyclic amines whose PKa values range from 2.95 to 9.17 were examined. Regardless of the base strengths, the heterocyclic amines except 4-aminopyridine afforded the addition products in a good yield in the nucleophilic reactions with 2a. 4-Aminopyridine (14) which afforded no addition product with 2a yielded ethyl N-(4-pyridyl) carbamate (16). Probably the nucleophilic substitution of 14 occurs at the ring nitrogen atom and the pyridinium salt (15) formed in the initial stage of the reaction rearranged intermolecularly and resulted in the formation of 16.

1-Alkoxycarbonyl-3-(2-thiazolyl) thioureas (A) were reacted with alkyl halides in presence of potassium carbonate to afford 1 (H)-alkoxycarbony1-2-alkyl-3-(2-thiazolyl)-isothioureas (D), 1-alkoxycarbony1-2-alkyl-3-(3-alkylthiazolin-2-ylidene) isothioureas (E) 2-alkylthio-thiazolo [3, 2-a]-s-triazine-4-ones (C). However, the rate of this reaction the yields of the products were dependent on the kinds of alkyl halide and thiazolyl thioureas (A). The cyclization products (C) were obtained in a good yield by the thermal treatment of the compounds (E).

The Reactions of ethoxycarbonyl isothiocyanate (23) with 4, 5-substituted 2-amino-thiazoles (24) afforded thiazolo [3, 2-a]-s-triazine-4-thio-2-ones (25), N-alkoxycarbonyl-N'-(2-thiazolyl)thioureas (26), alkyl-N-(2-thiazolyl)carbamates (27), ethyl-N-ethoxycarbonyl thiocarbamate (28) and thiocyanic acid (7). However, in the cases of the amines whose pKa values were smaller than that of 2-aminothiazole (24-a) or the amines which had some substituents on the 4-position of 24, the corresponding cyclic compounds (25) could not be obtained. A series of these phenomena was discussed in connection with basicities of 2-aminothiazoles (24) and the steric hindrance of the substituents on the 4-position of 24.

Dimethyl trithiocarbonate (4), which was formed as one of by-products in the preparation of α-acetylenyl xanthate (3), was obtained by treating 2-propynyl xanthate (10) or 3-phenyl-2-propynyl xanthate (18) with potassium xanthate (17). The reaction pathway for the formation of 4 from 18 was studied in detail, and the mechanism of the formation of dimethyl trithiocarbonate (4) and other by-products were consequently clarified.

The mechanism of the formation of 4-benzylidene-1, 3-dithiolane-2-thione (19) in the reaction of 4-benzylidene-1, 3-oxathiolane-2-thione (14) with sodium ethyl xanthate (15) became clear by the measurement of the radioactivity of 35S-4-benzylidene-1, 3-dithiolane-2-thione (32), which was synthesized by the treatment of 14 with 35S-sodium ethyl xanthate (29), and that of 35S-4-benzylidene-1, 3-dithiolane-2-one (38) which was obtained by the oxidation of 32 with mercuric acetate.

The reactions of some alkoxycarbonyl isothiocyanates (2) with 2-aminothiazol (15) afforded thiazolo[3, 2-a]-S-triazine-4-thio-2-one (27), N-alkoxycarbonyl-N'-(2-thiazolyl)-thuoureas (A), alkyl-N-(2-thiazolyl)carbamates (B), N-alkoxycarbonyl thiocarbamates (C) and thiocyanic acid (31). However, in the case using phenoxycarbonyl isothiocyanate (59), the corresponding 1 : 1 adduct of (59) and (15) could not be obtained, but thiazolo-[3, 2-a]-s-thiazine-2-thio-4-one (32) was isolated, besides the cyclic compound (27), thiazolyl carbamate (60) and phenol.

The reaction of sodium xanthates of prim-α-acetylenic alcohols and methyl iodide in an aprotic solvent gave corresponding xanthates. But in the case of propargyl alcohol, in addition to propargyl xanthate, dipropargyl thioncarbonate and dimethyltrithiocarbonate could be isolated.

The reaction of sodium alcoholates of sec- or tert- α-acetylenic alcohole having no ethynyl group with carbon disulfide in an aprotic solvent gave 4-alkylidene-1, 3-oxathiolane-2-thiones, but from alcohols having ethynyl group 4-methylidene-1, 3-dithiolane-2-thiones, or their rearranged isomers were mainly isolated, and in the case of 1-hexyn-3-ol (VI) or 1-ethynylcyclohexano 1 (XV) 4-methylidene-1, 3-oxathiolane-2-ones were also isolated.

The reaction of sodium alcoholates of prim. α-acetylenic alcohols and carbon disulfide in an aprotic solvent gave new heterocyclic compounds, 4-alkylidene-1, 3-oxathiolane-2-thiones and 4-alkylidene-1, 3-dithiolane-2-thiones.

N-Alkoxycarbonyl-N'-(2-thiazolyl) thioureas were reacted with some oxidants, such as bromine, benzoyl peroxide, hypobromous acid and N-bromosuccinimide, to afford 2-alkoxycarbonylimino-thiazolo [3, 2-b] thiadiazolines (X). Furthermore, from the reaction mixtures of N-ethoxycarbonyl-N'-(2-thiazolyl) thiourea (12) with bromine in chloroform, N-ethoxycarbonylimino-thiazolo [3, 2-b] thiadiazoline hydrobromide monohydrate (14) was obtained, which was easily dehydrobrominated to form 2-ethoxycarbonylimino-thiazolo-[3, 2-b] thiadiazoline (13) by treatment with large quantities of water. This paper describes particularly in detail about the structures of 13 and 14.

In the reaction of α-acetylenic alcohol and carbon disulfide, three compounds (4-alkylidene-1, 3-oxathiolane-2-thione, -1, 3-dithiolane-2-thione and -1, 3-oxathiolane-2-one) were obtained. In this paper it became clear that the formation of two compounds (V and VI) of them was due to the reaction of sodium α-acetylenyl xanthate (III) and IV by using 3-phenyl-2-propyn-1-ol. New 4-alkylidene-1, 3-dithiolane-2-thiones (XXIV and XXVI) were easily prepared from 4-alkylidene-1, 3-oxathiolane-2-thiones (XXIII and XXV) and commercially available potassium xanthate.