Synthesis of New Substituted 1,3-Diphenyl-5- chloropyrazoles Ibrahim Saad Abdel Hafiz,a Mohamed Ezz Eldin Rashad,b Mohamed Alaa Eldin Mahfouzb and Mohamed Hilmy Elnagdi*c aDepartment of Chemistry, Faculty of Education, Suez Canal University, Arish, Egypt bDepartment of Chemistry, Faculty of Science, South Valley University, Aswan, Egypt cDepartment of Chemistry, Faculty of Science, Kuwait University, P.O. Box 5969 Safat, 13060, Kuwait A number of new substituted 1,3-diphenyl-5-chloropyrazoles are prepared from 2-[(5-chloro-1,3-diphenyl-1H-pyrazol- 4-yl)methylene]malononitrile (2).In the last two decades we have developed several new syntheses of poly-functionally substituted aromatics and heteroaromatics utilizing activated nitriles as start- ing materials.14�}19 Thus, 5-chloro-1,3-diphenylpyrazole-4- carbaldehyde 1 condensed readily with malononitrile in ethanol to yield the corresponding ylidene 2 in excellent yield. Compound 2 reacted with 2-ethylidenemalononitrile 3a in re�Puxing ethanol to yield the product of addition and hydrogen cyanide elimination.This was thus formulated as the pyrazole derivative 7a and is assumed to be formed via the intermediacy of the Michael adduct 4 which readily cyclizes into 5 that loses HCN to yield 6, which then tautomerizes into 7a. The formation of 7a in this reaction parallels the reported formation of 2-aminobenzene-1,3- dicarbonitriles from the reactions of ylidenemalonitriles with 3.23,24 In contrast to the behaviour of 2 towards 3a, compound 3b reacted with 2 to yield 7b.Compound 7b is assumed to be formed via the intermediacy of the Michael adduct 4 which readily cyclizes to 5, which in turn tauto- merizes into 7b (Chart 1). The reaction of 2-methyl-2-pyrazolin-5-one (8a) with 2 a€orded the pyranopyrazole 9. In contrast to the reported formation of pyranopyrazoles 10 upon treatment of aryli- denemalononitrile 11 with substituted pyrazolones 8, we found that 8b,c reacted with 2 to yield 13a,b.These are assumed to be formed via the intermediacy of the Michael adduct 12 which then eliminates malononitrile, yielding 13 (Chart 2). Similar to the reported formation of phthalazines upon reacting 11 with ethyl 5-cyano-4-methyl-6-oxo-1-phenyl-1,6- dihydropyridazine-3-carboxylate (14), compound 14 reacted with 2 to yield the phthalazinone 18 which is assumed to be formed via the intermediates 15�}17 (Chart 3). It has been reported that 2-cyanomethyl-2-thiazolin-4-one 19a and ethoxycarbonylmethyl-2-thiazolin-4-one 19b react with 11 to yield 20 via addition of two molecules of 11 and elimination of one molecule of malononitrile.In contrast to this 19a,b reacted with 2 to yield only a 1:1 adduct. This was formulated as 21 rather than 22 based on the IR spectrum. The formation of 21 from 2 and 19 is assumed to proceed via initial formation of the Michael adduct 23. J. Chem. Research (S), 1998, 690�}691 J.Chem. Research (M), 1998, 2946�}2957 Chart 1 Chart 2 *To receive any correspondence. 690 J. CHEM. RESEARCH (S), 1998Similar to the behaviour of 19a,b, compound 19c also reacted with 2 to yield the adduct that is formulated as 21c and not 22c (Chart 4). The structure of the product of reaction of 24a±c with 11 is the subject of debate. Thus, some authors suggested25,26 structure 25 while others,27 believe that the formation of 26 occurs in this reaction. We have found that 24a±c react with 2 to yield the products of addition and subsequent cyclization, as indicated from the mass spectra.Thus, we believe that this product is 27a±c and is formed according to the sequence shown in Chart 4 (Chart 5). Techniques used: IR, 1H NMR, mass spectrometry and elemental analysis References: 27 Charts: 5 Table 1: Yields, mps, colour and elemental analysis for compounds 2, 7a,b, 9, 13a,b, 18, 21a±c and 27a±c Table 2: Spectral data for 2, 7a,b, 9, 13a,b, 18, 21a±c and 27a±c Received, 5th January 1998; Accepted, 28th July 1998 Paper E/8/00141C References cited in this synopsis 14 M.H. Elnagdi and A. W. Erian, Liebigs Ann. Chem., 1990, 1215. 15 N. S. Ibrahim, M. H. Mohamed, Y. Mahfouz and M. H. Elnagdi, J. Prakt. Chem., 1989, 331, 375. 16 M. H. Mohamed, N. S. Ibrahim, M. M. Hussien and M. H. Elnagdi, Heterocycles, 1988, 27, 1301. 17 S. A. S. Ghozlan, F. A. E. Abdel-Aal, M. H. Mohamed and M. H. Elnagdi, Z. Naturforsch., Teil B, 1986, 41, 489. 18 G. E. H. Elgomeie, H. A. Elfaham, S. Elgamal and M. H. Elnagdi, Heterocycles, 1985, 23, 1999. 19 M. H. Elnagdi, A. H. H. Elghandour, M. K. A. Ibrahim and I. S. A. Ha®z, Z. Naturforsch., Teil B, 1992, 47, 572. 23 N. S. Ibrahim, F. M. Abdel-Galil, R. M. Abdel-Motaleb and M. H. Elnagdi, Bull. Chem. Soc. Jpn., 1987, 60, 4486. 24 E. A. A. Hafez, Z. E. Kandeel and M. H. Elnagdi, J. Heterocycl. Chem., 1987, 24, 224. 25 S. M. Fahmy, N. M. Abed, R. M. Mohareb and M. H. Elnagdi, Synthesis, 1982, 490. 26 N. M. Abel, N. S. Ibrahim, S. M. Fahmy and M. H. Elnagdi, Org. Prep. Proced. Int., 1985, 17, 107. 27 K. U. Sadek, M. A. Selim, M. A. Elmaghraby and M. H. Elnagdi, Die Pharm., 1993, 48, 419. Chart 3 Chart 4 Chart 5 J. CHEM. RESEARCH (S)