Heterocyclization of compounds containing diazo and cyano groups. 2. Synthesis and recyclization of 4-substituted 5-amino-1,2,3-thiadiazoles

Switchable Synthesis of 4,5-Functionalized 1,2,3-Thiadiazoles and 1,2,3-Triazoles from 2-Cyanothioacetamides under Diazo Group Transfer Conditions

“…18 Signals of the ring and 4substituents in 1 H NMR spectra of compound 5 are slightly differed from those for triazole 4 allowing to estimate their ratio in reaction mixture. 13 The effect of a type and amount of a base on the process of rearrangement was studied by 1 H NMR spectrometry for transformation of thiadiazole 5m to triazole 17/4m in methanol in the presence of triethylamine and sodium ethoxide (Table 5).…”

“…1 H NMR (DMSO-d 6 /CHCl 3 ): δ 3.99 (s, 2H), 7.27−7.31 (m, 1H), 7.40−7.49 (m, 7H), 7.56 (d, J = 8.0 Hz, 2H). 13 Experimental Procedures for Preliminary Study of Interaction of Thioamide 1a with Tosyl Azide (2a) (Scheme 2). (A) Thioamide 1a (170 mg, 1.0 mmol) was added into cooled (+10 °C) solution of sodium ethoxide, freshly prepared from sodium (23 mg, 1.0 mmol) and anhydrous ethanol (4 mL), and the resulting solution was stirred at this temperature for 5−10 min.…”

“…1 H NMR (DMSO-d 6 /CHCl 3 ): δ 3.62−3.64 (m, 4H), 3.78−3.81 (m, 4H). 13 5-(Piperidin-1-yl)-1,2,3-thiadiazole-4-carbonitrile (3c). Compound 3c was obtained in 90% yield (228 mg) according to the general procedure A (thioamide 1c: 219 mg; 2 h) as a pale brownish oil; R f = 0.42 (EtOAc/PE, 1:2).…”

“…1 H NMR (CDCl 3 ): δ 1.70−1.83 (m, 6H), 3.63−3.66 (m, 4H). 13 C NMR (CDCl 3 ): δ 22.9, 25. down to +10 °C and tosyl azide (2a) (621 mg, 3.15 mmol) was added portion by portion. The resulting solution was stirred at +10 °C for 1.5 h, the solvent was removed under reduced pressure and the residue was purified by flash chromatography over silica gel (60−120) using EtOAc/PE (1:5) mixture to give aminonitrile 3c in 75% yield (450 mg) as a pale brownish oil; R f = 0.2 (EtOAc/PE, 1:5).…”

“…Therefore, the search of new routes to functionalized 1,2,3-triazoles remains a synthetic challenge. Since few 5- amino-1,2,3-triazole-4-carbothioamides 12 and 5-amino-1,2,3thiadiazoles 13 were prepared in reactions of aryl azides with 2-cyanothioacetamides we turned our attention to reaction of sulfonyl azides with cyanothioacetamides to find an approach to 1,2,3-triazoles bearing both thioamide and sulfonamide groups. At the same time, the reactions of primary and secondary methylene active thioamides with sulfonyl azides led to 5amino-1,2,3-thiadiazoles (Scheme 1).…”