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Keywords: 2.6-diaryl-4,4-dimethyl-4,5-dihydro-1H(3H)-indazolo [4,5-g]imidazoles. 4.5-dioxo-and 4-oxo-I -halophenyl-6.6-dimethyl-4,5.6.7-tetrahydroindazoles.Bearing in mind the importance of modifying a number of indazoles with the objective of preparing biologically active compounds 11-10], in continuation of work [111 we synthesized a series of I-halophenyl-4-oxo-4.5,6,7-tetrahydroindazoles and prepared some of their derivatives.We obtained the corresponding 2-hydrazinomethylene derivatives of dimedone (3) from the reaction of the potassium salt of 2-fomlyldimedone (1) with the hydrochlorides of 4-chloro-, 3-chloro-. 2-chloro-, 2,4-dichloro-, and 2.4-difluorophenylhydrazines (2). These compounds were converted into l-substituted 4-oxo-6,6-dimethyl-4.5.6.7-tetrahydroindazoles (4) on boiling in ethanol in the presence of hydrochloric acid. Oxidation of these ketones with selenious acid by a method 111, 12] gave the corresponding 4,5-dioxo-4.5,6,7-tetrahydroindazoles only with compounds 4a and 4b. Oxidation of the indazoles 4c-e by this method gave resinous products from which it was not possible to isolate pure products. Therefore we boiled the compounds in dioxane with selenious acid to oxidize the indazoles 4c-e. Resinous materials were fomled again but the individual products, separated by thin-layer chromatography, were shown to be the hydrated forms of the 4,5-dioxo derivatives by IR spectroscopy (two carbonyl frequencies in the 1730-1670 cm' region, absorptions at 3400-3100 cm '). Heating these for a short time at 160-170~ gave the individual cL-diketones 5c-e. Reaction of the 4,5-dioxo compounds 5a,c,e with equimolar anaounts of hydroxylamine, isonicotinic and salicylic acid hydrazides gave the corresponding carbonyl derivatives at the more electrophilic C,,,-carbonyl [11]. Reaction of the same c~-diketones 5a,c,e with o-phenylenediamine gave pyrazolo [4,3-alphenazines 7a,c,d. Reaction of the diketone 5a with 2.3-diaminopyridine gave a single reaction product which we ascribe the structure 3-(4-chlorophenyl)-5.5-dimethyl-4.5-dihydro-3H- lOazapyrazolo[4,phenazine (7b), since the amino group at C,,, in 2.3-diaminopyridine is the better nucleophile.

Earlier we modified indazoles in the reactions of 3-methyl-l-(2-pyridyl)-5-formyl-4-chloro-6,7-dihydroindazoles (I, II) with hydrazines, o-phenylenediamine, and certain C-nucleophiles [1]. In the present paper we discuss the reactions of the 3-chloroaldehydes (I-III) with guanidine, amidines, and hydroxylamine, leading to pyrazolo [5,4-h]quinazolines (IV-XII) and isoxazolo [5,4-e]indazole (XVII) respectively.When the chloroaldehydes (I, II) were boiled with guanidine carbonate, benzamidine hydrochloride, and 3-and 4-pyridinecarbamidine hydrochlorides in ethanol in the presence of sodium ethoxide, the corresponding 8-substituted 1-methyl-3-(2-pyridyl)-4,5-dihydropyrazolo[5,4-h]quinazolines (IV-IX) were obtained. 3-Methyl-l-phenyl-5-formyl-4-chloro-6,7-dihydroindazole (III) also reacts with 3-and 4-pyridinecarbamidines [2].The structure of the pyrazolo[4,5-d]quinazolines (IV-XII) is confirmed by the IR and PMR spectra (Table 1). Thus, the primary amino group of compound (IV) is characterized by the stretching vibrations at 3350 and 3150 cm -1, while the PMR spectrum contains a two-proton signal at t5 5.52 pprn.The reactions of the chloroaldehydes (I, II) with hydroxylamine hydrochloride in pyridine lead to the oximes (XIII, XIV). When boiled with acetic anhydride the chloroaldehydes (I, III) form the 4-acetoxy derivatives (XV) and (XVI). In the IR spectra of the enol acetates (XV) and (XVI) the carbonyl groups are characterized by absorption at 1774 (XV) and 1764 (XVI) cm -1. The treatment of 4-acetoxy-5-formylindazole (XV) with hydroxylamine leads to the isoxazolo[5,4-e]indazole (XVII).The aldoxime (XIII) is easily dehydrated to 3-methyl-l-(2-pyridyl)-4-chloro-5-cyano-6,7-dihydroindazole (XVIII) by boiling in acetic anhydride. Nucleophilic substitution of the chlorine atom in the latter is realized by the action of sodium alkoxide and also of potassium hydroxide and leads to the formation of the 4-ethoxy derivative (XIX) and 3-methyl-4-oxo-l-(2-pyridyl)-5-cyano-4,5,6,7-tetrahydroindazole (XX) respectively. The strong absorption band of the carbonyl group in the latter is found at 1686 cm -l, while vc__-N is formed at 2250 cm -1. The cyano ketone (XX) was also obtained by the action of hydroxylamine on 4-acetoxy-5-formylindazole (XV) in pyridine.

Reactionsof 1-(2-Pyridyl)-3-methyl-4-chloro-5-formyl-6,7dihydroindazole -[ring closure with guanidine, arylamidines, or hydroxylamine to pyrimidino-or isoxazoloindazoles, oxime formation and oxidation to the cyano derivative, nucleophilic substitutions at the indazole ring]. -(STRAKOVA, I. A.; DELYATITSKAYA, L. G.; PETROVA, M. V.; STRAKOV, A. YA.; Khim.

Synthesis and Reactions of 1-(2-Pyridyl)-3-methyl-4-chloro-5formyl-6,7-dihydroindazoles.-Vilsmeier formylation of 4-oxo-4,5,6,7-tetrahydroindazoles (III), obtained by cyclocondensation of 2-acetyl-3-hydroxycyclohexenone (I) with hydrazine (II), affords the title 4-chloro-5formyl-6,7-dihydroindazoles (V) which are subjected to reactions with various C-or N-nucleophiles. Thus, the hydrazines (VII) as well as C-H acids (XII) attack the formyl group, while in the presence of N,N-bisnucleophiles like free hydrazine or o-phenylenediamine (X) a cyclocondensation takes place to furnish the pyrazolo-(IX) or benzodiazepino-fused indazoles (XI), respectively. -(STRAKOVA, I. A.; DELYATITSKAYA, L. G.; PETROVA, M. V.; STRAKOV, A. YA.; Khim.