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Synthesis of triazolo[4,3-b] [1,2,4,5]tetrazines and triazolo[3,4-b][1,3,4] thiadiazines using chitosan as heterogeneous catalyst under microwave irradiation

“…The structure of the isolated products was unambiguously established by spectral data (MS, IR, 1 H NMR) and its elemental analyses (see experimental). For example, the IR spectrum of 5a showed two characteristic bands at υ 3222 and 1740 cm -1 assignable for NH and COOEt groups respectively and the 1 H NMR spectra showed, in each case, one characteristic singlet signal at δ 9.24 ppm 24 assignable to the tetrazine NH. Also 1 H NMR spectra revealed the absence of NH 2 signal which appear at δ 4.8 ppm 25 of compound 1.…”

Reactions of nitrilimines with heterocyclic amines and enamines. Convenient methodology for synthesis and annulation of heterocycles

“…30 Although, four possible tautomeric structures A-D can be written for each of the compounds 28 ( Figure 1), they were found to exist predominantly in the indicated tautomeric form 28A. This structural assignment was based on the similarity of their electronic absorption spectra with those reported for the azo chromophore [31][32][33] …”

Reactions of hydrazonoyl halides with heterocyclic thiones. Convenient methodology for heteroannulation, synthesis of spiroheterocycles and heterocyclic ring transformation

“…Reactions of hydrazonoyl halides with either 3-amino-2,3-Dihydro-6-substituted-2-thioxopyrimidin-4(3H)-ones 48 or 3-amino-6-substituted -2,3-dihydro-2-methylthio-4(3H)-pyrimidinone 49 were recently reported by Shawali et al [42][43][44] to give the respective 4H- Very recently Shawali et al 47 reported that reaction of hydrazonoyl halides with either 4- . 48 The reaction was said to be completely peri and regioselective.…”