710 ISSN 1070-3632, Russian Journal of General Chemistry, 2020, Vol. 90, No. 4, pp. 710–719. © Pleiades Publishing, Ltd., 2020. Reactions under Pressure: Synthesis of Functionally Substituted Arylhydrazonal Derivatives as Precursors of Novel Pyridazines and Nicotinates K. M. Al Zaydi a,b, *, M. A. Al-Johani a,c , N. F. Alqahtani a,b , S. M. Mousally a,b , and N. Hilmy Elnagdi d a Department of Chemistry, Faculty of Sciences–AL Faisaliah, King Abdulaziz University, Jeddah, 21533 Saudi Arabia b Chemistry Department, Faculty of Sciences, University of Jeddah, Jeddah, 21589 Saudi Arabia c College of Science at Yanbu–Taibah University, Almadinah Almunawarah, Almadinah, 41477 Saudi Arabia d Faculty of Pharmacy, Modern University for Technology and Information, Cairo, 11571 Egypt *e-mail: kmalzaydi@uj.edu.sa Received February 17, 2020; revised April 3, 2020; accepted April 10, 2020 Abstract—Q-tube assisted multicomponent synthesis of novel arylhydrazonals, pyridazines and nicotinates has been explored. The target molecules have been prepared via one pot reaction of arylhydrazonals with activated methylene nitriles in either ethanolic piperidine, dimethyl acetylene dicarboxylate (DMAD), 1,4-diazobicyclo[2.2.2]- octane (DABCO), or Ph 3 P under pressure. Such conditions make reaction time much shorter and yields higher as compared with those conducted under conventional conditions. The structures of products have been determined by X-ray crystallography and spectroscopic methods. Keywords: arylhydrazonals, Q-tubes, pyridazines, nicotinates, reactions under pressure, green chemistry DOI: 10.1134/S1070363220040234 INTRODUCTION Reactions under pressure in Q-tubes have proven to be a faster and cleaner approach to chemical transformations thus addressing most of the green chemistry principles [1]. To date, there are more than 50 papers devoted to the successful use of high pressure processes in Q-tubes [2]. In this study, we have developed a new general approach to synthesis of functionally substituted 2-arylhydrazonals 3 as precursors for biologically active pyridazine and nicotinate derivatives utilizing Q-tubes. Their reactivity with malononitrile, ethyl 2-cyanoacetate and 3-oxo-3- phenylpropanenitrile under pressure in ethanol/piperidine and dimethylacetylenedicarboxylate (DMAD) in the presence of DABCO or Ph 3 P is studied. The products formed under pressure have been compared with those formed upon conventional heating, microwave or ultrasound irradiation. EXPERIMENTAL Melting points were measured on a Gallenkamp Electrothermal melting point apparatus and are uncorrected. IR spectra were recorded on an 80486-pc FTIR Shimadzu spectrophotometer using KBr pellets. NMR spectra were measured on a Varian Mercury VX- 300 NMR spectrometer using CDCl 3 or DMSO-d 6 as solvents. Chemical shifts were referenced to the solvent signals. IR and NMR spectral data were collected at the Micro analytical Center, Cairo University, Egypt. Elemental analysis was carried out on a Perkin–Elmer 2400 Analyzer. Mass spectra were measured on a MS- 5988 GS-MS Hewlett–Packard spectrometer, EI technique at 70 eV. Elemental analysis and MS were carried out at the Regional Center for Mycology and Biotechnology, Al-Azhar University, Cairo, Egypt. X-ray crystallography analysis was carried out on a Kappa CCD Enraf Nonius FR 590 diffractometer at the National Research Center, Dokki, Cairo, Egypt. Microwave irradiation experiments were carried out using a Monowave 300 single-mode Anton Paar GmbH microwave reactor. Ultrasonication was carried out with a microprocessor controlled-2004, high-intensity ultrasonic processor (750 W). Q-Tube- assisted reactions were performed in a Q-tube-safe pressure reactor, Q Labtech. General procedure for arylhydrazonals 3j, 3k, 3l, 3m. Cold solutions (0–5°C) of compounds 2a–2d were prepared by adding cold solution of sodium nitrite (1 g in 10 mL of H 2 O) to cold solution of 10 mmol of aryl amine 2Aa–2Ad in 5 mL of conc. HCl upon stirring.