Vilsmeier–Haack reaction of (E)-1-(1-(3,5-difluorophenyl)ethylidene)-2-phenylhydrazine (1) using dimethyl formamide in excess of phosphorous oxychloride by conventional method, resulted in the synthesis of title compound 3-(3,5-difluorophenyl)-1-phenyl-1H-pyrazole-4- carbaldehyde (2) in good yield and high purity. Structure characterization of the novel title compound was done by IR, ¹H NMR, ¹³C NMR and mass spectral analysis.

Now day; the interest for the synthesis of heterocyclic compounds containing hydroquinoline fragments has increased tremendously due to their wide variety of pharmaceutical and industrial applications. This work details the synthesis of linear and fused heterocyclic systems containing hydroquinoline fragments and the pharmacological activity spectra of the synthesized compounds was predicted by in silico method using Prediction of Activity Spectra of Substances (PASS) program. 1,2,2,4-tetramethyl-1,2-dihydroquinoline-6-carbaldehyde 5a was reacted for three hours with a system of hydroxylammonium chloride/pyridinium chloride/toluene to produce 1,2,2,4-tetramethyl-1,2-dihydroquinoline-6-nitrile 7. N-benzyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde 6b and iodine reacted at room temperature in aqueous ammonia water, followed by aq. treatment with Na2S2O3 and produced N-benzyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline-6-nitrile 8. 30-60% 2-phenyl-1,3-oxazol-5(4H)-ones 9a,b; 10a,b were synthesized via the condensation reaction of N-alkylhydroquinoline-6-carbaldehydes 5a,b; 6a,b with hippuric acid in acetic acid. When activated 7-methylazolopyrimidines 11a,b were reacted with N-alkyl-2,2,4-trimethyl-1,2,3,4-tetrahydroquinoline-6-carbaldehydes 6a,b, the reaction produced 60–70% yield of 7-[(E)-2,2,4-trimethylhydroquinolin-6-ylidenemethyl]azolo[1,5-a]pyrimidin-6-yl carboxylic acids 12a,b. The condensation reaction of 7-hydroxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline 3h with dimethylacetylenedicarboxylate (DMAD) and ethylacetoacetate afforded methyl (Z)-2-(5,7,7,8-tetramethyl-2-oxo-7,8-dihydrofuro[3,2-g]quinolin-3(2H)-ylidene)acetate 16 and 4,6,8,8,9-pentamethyl-8,9-dihydro-2H-pyrano[3,2-g]quinolin-2-one 17, respectively. The condensation reaction of 6-formyl-7-hydroxy-1,2,2,4-tetramethyl-1,2-dihydroquinoline 5e with methylene active compounds ethylcyanoacetate/dimethyl-3-oxopentanedioate/ ethylacetoacetate/diethylmalonate/Meldrum’s acid afforded 3-substituted dihydroquinoline containg coumarins 19 & 21. A pentacyclic coumarin 22 was obtained via the random condensation reaction of malononitrile with 5e in the presence of catalytic amount of piperidine in ethanol. The potential biological activities of the synthesized compounds were evaluated using PASS computer program. According to the prognosis, (E)-4-(N-alkylhydroquinolin-6-yl)-3-buten-2-ones, 13a, b & 14 showed high probability of being active (Pa) as the Gluconate 2-dehydrogenase inhibitor, Anti-allergic, Anti-asthmatic, and Anti-arthritic with the Pa value of 0.849-0.870. It was also found out that hydroquinolinecarbonitrile compounds 7 & 8 have a propensity to act as a good progesterone antagonists, anti-allergic, anti-asthmatic, and anti-arthritic (Pa = 0.276-0.827). Among the coumarin moieties containing hydroquinolines, compounds 17, 19a, and 19c were predicted to be good progesterone antagonists with the Pa values of 0.710, 0.630 and 0.615; respectively.