Synthetic Studies on Antituberculous Agent. VIII. Reaction between 4-Picoline and Aromatic Primary Amines in the Presence of Sulfur.

From N‐Substituted Thioamides to Symmetrical and Unsymmetrical 3,4,5‐Trisubstituted 4H‐1,2,4‐Triazoles: Synthesis and Characterisation of New Chelating Ligands

“…[41] This compound had previously only been obtained in an acceptable yield of 57% from the reaction of 2-methylpyridine, sulfur and 4-aminopyridine in a pressure vessel at 200°C, while carrying [b] (from 4-nitroaniline) [34] 21% [b] (from 4-nitroaniline) [38] 40% [b] (from 4-nitroaniline) [39] 47% [a] (from 1,4-phenylenediamine) [37] 80% 4-pyridyl (5) 14% [b] (from 4-aminopyridine) [41] 57% [c] (from 4-aminopyridine) [41] 77% 4-methylphenyl (6) 30% [b] (from 4-nitrotoluene) [34] 55% [b] (from 4-methylaniline) [42] 14% [b] (from 4-methylaniline) [43] 79% 2,4,6-trimethylphenyl (7) 65% [b] (from 2,4,6-trimethylaniline) [44] 74% methyl (8) 17% [b] (from methylamine hydrochloride) [45] 50% [b] (from N-methylformamide) [36] 34% [d] (from N-methylformamide) [46] 69% [a] Reaction carried out in the presence of a catalytic amount of sodium sulfide nonahydrate with the appropriate amine.…”

“…To test the general applicability and efficiency of these modified reaction conditions (i.e. sulfur/amine ratio of 3:1, large excess of 2-methylpyridine, 2 mol % sodium sulfide nonahydrate, reflux at ambient pressure), the synthesis of another two N-arylpyridine-2-thiocarboxamides, namely N-(4-methylphenyl)pyridine-2-thiocarboxamide (6) [34,42,43] and N- (2,4,6-trimethylphenyl)pyridine-2-thiocarboxamide (7), [44] was carried out (Scheme 4). In these two cases the modified reaction conditions also proved to be superior to earlier protocols, the yields of the recrystallised products being 79 and 74%, respectively (Table 1).…”

Transition-Metal-Free Synthesis of 2-Substituted Benzothiazoles from Nitrobenzenes, Methylheteroaryl Compounds, and Elemental Sulfur, Based on Nitro-Methyl Redox-Neutral Cyclization

“…Eluent, hexane/ethyl acetate = 3:1; pale yellow powder, 170 mg, 54% yield; mp: 133–134 °C (lit . 132–134 °C); FT-IR (diamond ATR): 1591, 1474, 1408, 1254, 1213, 978, 822, 756, 727, 702, 476 cm –1 ; 1 H NMR (600 MHz, CDCl 3 ): δ 8.78 (dd, J = 1.4, 4.1 Hz, 2H), 8.14 (d, J = 7.6 Hz, 1H), 7.96–7.95 (m, 3H), 7.55 (t, J = 7.6, 1H), 7.47 (t, J = 7.6 Hz, 1H); 13 C­{ 1 H} NMR (151 MHz, CDCl 3 ): δ 165.3, 154.1, 150.9, 140.6, 135.4, 127.0, 126.4, 124.1, 122.0, 121.3.…”

“…Eluent, hexane/ethyl acetate = 3:1; yellowish brown powder, 162 mg, 48% yield; mp: 167–169 °C (lit . 167–169 °C); 1 H NMR (600 MHz, CDCl 3 ): δ 8.76 (dd, J = 1.7, 4.2 Hz, 2H), 8.00 (d, J = 8.3 Hz, 1H), 7.93 (dd, J = 1.7, 4.2 Hz, 2H), 7.74 (s, 1H), 7.36 (d, J = 8.9 Hz, 1H), 2.52 (s, 3H); 13 C­{ 1 H} NMR (151 MHz, CDCl 3 ): δ 164.1, 152.3, 150.8, 140.8, 136.7, 135.6, 128.7, 123.5, 121.7, 121.2, 21.8.…”

“…Eluent, hexane/ethyl acetate = 1:1; yellow-white powder, 34 mg, 9% yield; mp: 153–155 °C (lit . 158–159 °C); FT-IR (diamond ATR): 1590, 1484, 1413, 1263, 1215, 1022, 817, 592, 498 cm –1 ; 1 H NMR (600 MHz, CDCl 3 ): δ 8.74 (dd, J = 1.4, 4.1 Hz, 2H), 8.00 (d, J = 8.9 Hz, 1H), 7.90 (dd, J = 1.7, 4.8 Hz, 2H), 7.38 (d, J = 2.1 Hz, 1H), 7.15 (dd, J = 2.4, 8.4 Hz, 1H), 3.91 (s, 3H); 13 C­{ 1 H} NMR (151 MHz, CDCl 3 ): δ 162.5, 158.7, 150.8, 148.7, 140.8, 136.9, 124.6, 121.1, 116.7, 104.2, 56.0.…”