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Microwave Synthetic Technology
Published in Banik Bimal Krishna, Bandyopadhyay Debasish, Advances in Microwave Chemistry, 2018
Biswa Mohan Sahoo, Bimal Krishna Banik, Jnyanaranjan Pa
Synthesis of benzothiazole derivatives (BT-1 to BT-10) are carried out from 2-aminothiophenol, aromatic aldehyde and phenyl iodonium bis-trifluoroacetate (PIFA) in ethanol. The synthesized compounds are subjected to antimicrobial screening by estimating the minimum inhibitory concentration (MIC) by adopting the serial dilution technique. All the synthesized newer benzothiazole derivatives (BT-1 to BT-10) are evaluated in terms of analgesic activity by tail immersion test. All the tested compounds displayed varying degrees of analgesic activity. Benzothiazole derivatives bearing pyrazolyl system exhibited comparable or slightly less potent activity than the standard pentazocine. The results of the study are given in Tables 11.12 and 11.13 [120].
New potential fungicides pyrazole-based heterocycles derived from 2-cyano-3-(1,3-diphenyl-1H-pyrazol-4-yl) acryloyl isothiocyanate
Published in Journal of Sulfur Chemistry, 2021
Sayed K. Ramadan, Nasser A. Ibrahim, Sarah A. El-Kaed, Eman A. E. El-Helw
Interaction of isothiocyanate derivative 2 with 2-aminothiophenol, 2-aminoaniline, 2-hydroxybenzoylhydrazine, and thiourea in boiling acetonitrile achieved benzothiazole, pyrimidinethione, and acylthiourea derivatives 13-16, respectively (Scheme 3). The IR spectrum of 13 showed NH, C≡N, and C = O absorptions at ν 3142, 2216, and 1677 cm−1, respectively. Also, its 1H NMR spectrum disclosed two singlet signals for C5-H pyrazole (at δ 9.19 and 9.15 ppm), and two singlet signals for olefinic proton (at δ 8.32 and 8.08 ppm) which showed its existence as a mixture of E- and Z-isomers in a ratio of 1:1. Furthermore, its mass spectrum displayed the molecular ion peak at m/z 447 (53%) and the base peak fragment at m/z 77 corresponding to phenyl cation, as well as some important fragments. Formation of benzothiazole derivative 13 was distinctly interpreted via cyclization of thiourea intermediate [I] by removing gaseous hydrogen sulfide molecule, as detected by the change in color of lead acetate paper into black. The 1H NMR spectrum of 14 displayed an exchangeable singlet integrated to two protons of the primary amino group and showed its existence as a mixture of cis and trans isomers in a ratio of 1:1 by showing four doublet signals corresponding to vicinal CH–CH protons. The IR spectrum of 15 showed OH, NH, C≡N, and C = O absorptions at ν 3403, 3203, 2205, and 1686 cm−1, respectively. Moreover, its 1H NMR spectrum displayed four exchangeable singlet signals corresponding to one OH and three NH protons at δ 12.32, 11.80, 11.20, and 10.91 ppm. The IR spectrum of 16 retained the nitrile and carbonyl functionalities. Its 1H NMR spectrum exhibited three exchangeable singlet signals corresponding to two NH and NH2 protons. In contrast, treating 2 with hydrazinecarbothiohydrazide at room temperature furnished the triazolopyrimidine derivative 17 which can be visualized via Scheme 4. The IR spectrum of 17 conserved both nitrile and carbonyl functionalities. The existence of exchangeable singlet signals for NH and NH2 protons and the absence of singlet signal of the olefinic proton in its 1H NMR spectrum supported the assigned structure. Furthermore, its mass spectrum displayed the M+. peak at m/z 426 (6%) and a fragment at m/z 77 as a base peak corresponding to phenyl cation (cf. Experimental).