Reaction of thiocarboxanilide derivatives of 2-phenylimino-3-phenyl-4-thiazolidinone and 1,3-diphenyl-2-thioxo-4-imidazolone with hydrazonoyl halides and active chloromethylene compounds

The potassium salts of thiocarboxanilide of 2phenylimino-3-phenyl-4-thiazolidinone and 1,3diphenyl-2-thioxo-4-imidazolone react with hydrazonoyl halides in N,N-dimethylformamide to afford the corresponding 1,3,4-thiadiazoline derivatives. 2-Phenylimino-3-phenyl-4-thiazolidinone reacts with active chloromethylene compounds in N,N-dimethylformamide to give the corresponding thiazolylidenethiazolidin-4-one derivatives. The new compounds were characterized using IR, H NMR, C NMR and mass spectra.


RESULTS AND DISCUSSION
The intermediates 4A (Ar' = ph) and 4B (Ar' = 4-CH 3 C 6 H 4 ) were prepared by the reaction of 2-phenylimino-3-phenyl-4-thiazolidinone 2 with arylisothiocyanate 3A,B in dimethylformamide in the presence of potassium hydroxide (Scheme 1).Treatment of 4A with hydrazonoyl halides 1a-e in dimethylformamide afforded, in each case, one isolable product as evidenced by TLC analysis of the crude products.Both mass and elemental Scheme 1.
analyses data of the products isolated are compatible with the two possible structures 7 and 10 (Scheme 1).However, the latter structure 10 was discarded as the reaction products were recovered unchanged after treatment with mercuric oxide in boiling acetic acid while the treatment is expected to convert 10 -if present-to 12, the C = S double bond is known to be more reactive dipolarophile than the C = C double bond [43], and reaction of acyclic β-ketothioanilides with 1 has been reported to give 2-alkylidene derivatives [44].Accordingly, the product isolated from reaction 1a with 4A or 4B is assigned structure 7.This assignment was substantiated by the finding that reactions of 1a with either 4A or 4B yield one product which is the same in both cases indicating the elimination of an arylamine molecule during the reaction to give 7.To account for the formation of 7 it is suggested that the reaction starts with the formation of thiohydrazonate ester 5 followed by intramolecular cyclization to give 6 which in turn eliminated arylamine to give 7.
Stereochemically, the isolated products can have either the 7 or 11 configurations.Molecular models indicate that structure 11 suffers severe steric interactions due to the close proximity of N-aryl group and C = O group.On this basis we suggest that the configuration of the products isolated is the less hindered structure 7.
Similarly, treatment of 1,3-diphenyl-2-thioxo-4-imidazolinon-5-thiocarboxanilide 14A (prepared by the reaction of 1,3-diphenyl-2-thioxo-4-imidazolone 13 with phenylisothiocyanate 3A in dimethylformamide in the presence of potassium hydroxide) with hydrazonoyl halides 1a-c,f-j afforded a single product in each case and was assigned structure 15 (Scheme 2).The structure of the latter products was established on the basis of its elemental analysis and spectroscopic data (Experimental).The IR spectrum of the isolated product 15a, taken as example, revealed the appearance of ring carbonyl absorption band near 1670 cm -1 in addition, its mass spectrum revealed a peak corresponding to the molecular ion m/z 504.
In the course of the previous reaction it was found that the reaction proceeds via elimination of an arylamine to give the product.This finding promoted us to perform the reaction of 4A with active α-chloromethylene compounds 16a-e to investigate if such reaction will lead to thiazoline 19 and/or 1,3-oxathiol 20.Previous literature reports indicated that the reaction of active α-chloromethylene compounds of simple ketones and nitriles with potassium salts of acyclic thioanilide gave the thiazoline derivatives [45], while with cyclic thioanilide gave 1,3-oxathiol derivatives [28].
Treatment of 4A with ethyl 2-chloro-3-oxobutanoate 16a in dimethylformamide afforded a single product as evidenced by TLC and 1 H-NMR of the crude products (Scheme 3).
Both elemental and spectroscopic analyses data were found compatible with 2,3-dihydro-3-phenylthiazole derivatives structure 19 and not the 1,3-oxathiol-2-ylidene derivatives 20 we reported earlier [28].Compound 4A reacted similarly with varieties of active α-chloromethylene compounds 16b-e and gave the corresponding 19b-e respectively.The reaction pathway that seems to account for the formation of 19 from 5 and 16 is outlined in Scheme 3. It is proposed that the reaction involves nucleophilic substitution to give 17.Cyclization of the latter product leads to the formation of 18 which loses the elements of water to give 19.These products can be assigned one of the two stereoisomeric structures (Z)-19 or (E)-19 (Scheme 3).The present data cannot distinguish between these two isomers, however.The elemental analyses and IR spectroscopic data of compounds 19 were consistent with the assigned structures.The structures of the 19 were also ascertained by the 1 H NMR,

CONCLUSIONS
The reaction of hydrazonoyl halides 1a-k with thiocarboxanilide derivatives 4 and 14 gave the corresponding 1,3,4-thiadiazole derivatives 7 and 15 similar to the products previously obtained with different thiocarboxanilide derivatives [27].The reaction of active α-chloromethylene ketones with thiocarboxanilide derivatives gave the thiazoline derivatives 19, contrary to the previous finding we have reported [28] which gave 1,3-oxathiol derivatives.

13 C
NMR and MS measurements (Experimental).