Studies in the Pyrazolidine Field

Section I. Cyclisation of cyanoacetylhydrazobenzene (LXVI) or the reaction of ethyl cyanoacetate with hydrazobenzene gave 3-imino-5-oxo-l,2-diphenylpyrazolidine (LXV) and its pp'-dimethyl derivative (LXVIII). (LXV) and its 4-methyl derivative (LXX) were best prepared by the action of potassium cyanide on the appropriate a-haloacylhydrazobenzene. Ring opening studies have been made on 3-imino-5-oxo-1,2-diphenyl-pyrazolidine (LXV), which has also been converted into 3,5-dioxo-1,2-diphenylpyrazolidine (XIV). Ethanolic hydrochloric acid hydrolysis of (LXV) and (XIV) opened the pyrazolidine ring giving the same products, namely N-(beta-carboxyacetyl)-hydrazobenzene (LXXII; R = H) and its ethyl ester (LXXII; R = Et); the latter compound was cyclised to (XIV) using alkali. 3-Imino-5-oxo-1,2-diphenylpyrazolidine (LXV) condensed with eyclo-hexanone giving 4-cyclohexenyl-3-imino-5-oxo-1,2-diphenylpyrazoli-dine (LXXIV) which on catalytic hydrogenation yielded 4-cyclohexyl -3-imino-5-oxo-1,2-diphenylpyrazolidine (LXXV). Acid treatment of the latter converted it into the corresponding 3,5-dioxo-compound. The 4-isonitroso derivative (LXXIX) and the 4-phenyl-azo derivative (LXXX) of 3-imino-5-oxo-1,2-diphenylpyrazolidine (LXV) were also prepared. Reduction of the former gave 3,4-diamino-5-oxo-1,2-diphenylpyrazoline (LXXXIb) which on condensation with diacetyl and benzil gave 5,6-dimethyl-3-oxo-1,2-diphenylpyrazolo-[2,3b]-pyridazine and 3-oxo-1,2,5,6-tetraphenyl-pyrazolo-[2,3b]-pyridazine respectively. Section II. Acetylation of 3-imino-5-oxo-1,2-diphenylpyrazolidine (LXV) using acetic anhydride gave 3-acetylimino-5-oxo-1,2-diphenylpyrazolidine (XCI) and 4-acetyl-3-imino-5-oxo-1,2-diphenyl-pyrazolidine (LXXXIX). The latter could also be prepared exclusively using acetyl chloride-pyridine. (LXV) was also converted into its N-butyryl derivative. The N-acetyl derivative (XCI) was readily hydrolysed to (LXV) using alkali but the 4-acetyl derivative (LXXXIX) was stable to alkaline hydrolysis. Acetic anhydride on 3-imino-5-oxo-1,2-diphenylpyrazolidine (LXV) also gave a mixed crystal of (LXV) and (XCI). The N-monoacetyl compound (XCI) was acidic and on treatment with diazomethane N-methylation took place yielding 3-acetylmethylamino-5-oxo-1,2-diphenylpyrazoline (CV); the latter on alkaline hydrolysis gave 3-methylimino-5-oxo-1,2-diphenylpyrazolidine (CVI). 4-Cyano-acetyl-3-imino-5-oxo-1,2-diphenylpyrazolidine (CX) was also prepared and acid hydrolysis converted it into 4-acetyl-3-imino-5-oxo-lf2-diphenylpyrazolidine (LXXXIX). On treatment with alkali 4-cyanoacetyl-3-imino-5-oxo-1,2-diphenylpyrazolidine was cyclised to the isomeric 6-amino-4-hydroxy-3-oxo-1,2-diphenyl-pyrazolido-[2,3b]-pyridine (CXI). The latter on treatment with diazomethane afforded 6-amino-4-methoxy-3-oxo-1,2-diphenylpyrazo-lido-[2,3b]-pyridine (CXIII) which was also formed by successive reaction of (CX) with diazomethane to give 3-imino-4-(alpha-methoxy-(beta-cyanovinyl)-5-oxo-1,2-diphenylpyrazolidine (CXII), followed by heating to 200. 3-Imino-4-methyl-5-oxo-l,2-diphenyl-pyrazolidine (LXX) on acetylation gave an N-acetyl derivative (CXV) and 5-acetoxy-3-acetylimino-4-methyl-1,2-diphenylpyrazoline (CXVIII). Both (CXV) and (CXVIII) on alkaline hydrolysis yielded the parent pyrazolidine (LXX). 3-Acetylimino-4-cyclohexyl-5-oxo-1,2-diphenylpyrazolidine (CXXII) was also prepared. Treatment of 3,4-diamino-5-oxo-1,2-diphenylpyrazoline (LXXXIb) with acetic anhydride gave 4-acetylamino-3-imino-5-oxo-1,2-diphenyl-pyrazolidine (CXXIV), which could also be prepared by the reaction of the diamino-compound (LXXXIb) with acetyl chloride at room temperature. On refluxing (CXXIV) with acetyl chloride, 3,4-diacetylamino-5-oxo-1,2-diphenylpyrazoline (CXXVII) was produced. 4-Formylamino-3-imino-5-oxo-1,2-diphenylpyrazolidine was obtained from the action of formic acid on (LXXIb)