Photodesulfurization of 2,4-Diaryl-1,2,4-triazole-3-thiones 271
128.5, 128.7, 129.9, 130.9, MS m/z (%) 281 (M+, 20),
280 (4), 163 (4), 132 (3), 131 (4), 91 (4), 77 (10). Anal.
Calcd for C16H15N3S: C, 68.29; H, 5.37; N, 14.43.
Found: C, 67.84; H, 5.40; N, 14.92.
MS m/z (%) 267 (M+, 52), 266 (100), 234 (40), 233
(40), 207 (3), 131 (20), 103 (75), 91 (90), 77(50).
Anal. Calcd for C15H13N3S: C, 67.38; H, 4.90; N, 15.71.
Found: C, 67.42; H, 4.97; N, 15.80.
4-(1-Naphthyl)-5-(o-tolyl)-1,2,4-triazole-3-thione
(1c). Yield: 62%; mp 244–246◦C (CHCl3); IR (KBr)
3078, 2921, 2748, 1508, 1330 cm−1; UV (MeOH) 222,
General Procedure for 4,5-Diaryl-1,2,4-triazoles
2a–e
1
258 nm; H NMR (200 MHz, CDCl3) δ 2.3 (s, 3H,
A solution of triazole-3-thione 1 (250–500 mg) in ab-
solute methanol (180 ml) was irradiated in a thin-
film reactor (equipped with one lamp) at 254 nm
for 1–1.5 h. The solution was pumped from a three-
necked RB flask through a jet, which allows a thin-
film to fall over a quartz tube surrounding the lamp.
A thin stream of nitrogen gas was passed through
the reaction mixture during the reaction. After the
completion of the reaction (monitored by TLC),
the solvent was evaporated under vacuum and the
residue chromatographed and eluted with ethyl ac-
etate/petroleum ether mixture (2:3–4:1) to give the
triazole 2.
CH3), 6.9–7.9 (m, 11H, ArH), 12.3 (s, 1H, SH); 13C
NMR (50 MHz, CDCl3)δ 20.23 (CH3), 123.40, 124.71,
125.12, 125.42, 126.88, 127.14, 127.58, 128.55,
128.73, 129.61, 129.70, 130.19, 130.49,130.67,
134.16, 138.12, 152.17 (C N), 169.03 (C S), MS
m/z (%) 317 (M+, 100), 284 (20), 258 (3), 185 (4), 140
(16), 132 (7), 127 (12), 117 (4), 116 (12), 91 (9), 77
(10). Anal. Calcd for C19H15N3S: C, 71.89; H, 4.76; N,
13.23. Found: C, 71.73; H, 4.92; N, 13.26.
5-(4-Pyridyl)-4-(p-tolyl)-1,2,4-triazole-3-thione (1d).
Yield: 40%; mp 238–240◦C (EtOH); IR (KBr) 3136,
2931, 2738, 1602, 1574, 1427 cm−1; UV (MeOH)
260, 312 nm; 1H NMR (200 MHz, CH3OH-d4) δ
2.44 (s, 3H, CH3), 7.21–7.39 (m, 6H, ArH), 8.49–
8.52 (m, 2H, ArH); 13C NMR (50 MHz, CH3OH-
d4) δ 20.29, 122.55, 128.35, 130.46, 132.13, 135.20,
141.12, 149.75, 157.00 (C N), 170.10 (C S); 13C
NMR-DEPT 90 (50 MHz, CDCl3) δ 119.20, 122.55,
128.36, 130.46, 149.75, MS m/z (%) 268 (M+, 100),
267 (85), 235 (2), 209 (15), 181 (7), 163 (15), 131
(10), 119 (8), 105 (15), 104 (12), 91 (24), 78 (10), 77
(5). Anal. Calcd for C14H12N4S: C, 62.66; H, 4.50; N,
20.87. Found: C, 62.87; H, 4.72; N, 20.89.
5-Phenyl-4-(p-tolyl)-1,2,4-triazole (2a). mp 142–
144◦C (CHCl3) (Lit. [22] mp: 140◦C); UV (MeOH)
1
209 nm; IR (KBr) 1517 cm−1; H NMR (200 MHz,
CD3CN) δ 2.37 (s, 3H, CH3), 7.15–7.45 (m, 9H, ArH),
8.38 (s, 1H, CH); 13C NMR (50 MHz, CD3CN) δ
20.56, 126.33, 127.59, 128.87, 129.02, 130.09, 130.55,
132.73, 140.01, 145.54 (C3 CH), 156.30; 13C NMR-
DEPT 90 (50 MHz, CDCl3) δ 126.33, 128.88, 129.02,
130.09, 130.55, 145.55 (C3 CH).
4,5-Di-(p-tolyl)-1,2,4-triazole (2b). mp 185–187◦C
(CHCl3); IR (KBr) 1515 cm−1; UV (MeOH) 206 nm;
1H NMR (400 MHz, CDCl3) δ 2.32 (s, 3H, CH3), 2.42
(s, 3H, CH3), 7.06–7.41 (m, 8H, ArH), 8.26 (s, 1H,
CH); 13C NMR (50 MHz, CDCl3) δ 21.7, 21.9, 124.2,
126.1, 129.0, 129.8, 131.0, 132.8, 140.1, 140.5, 145.3
(C3 CH), 153.90 (C N); 13C NMR-DEPT 135 (50
MHz, CDCl3) δ 21.7 (CH3), 21.9 (CH3), 126.1, 129.0,
129.8, 131.0, 145.3 (C3 CH), MS m/z (%) 249 (M+,
100), 248 (91), 221 (3), 132 (3), 131 (8), 118 (4), 117
(2), 104 (12), 91 (42), 90 (10), 77 (36). Anal. Calcd
for C16H15N3: C, 77.08; H, 6.06; N, 16.85. Found: C,
77.28; H, 5.97; N, 16.91.
4-Benzyl-5-phenyl-1,2,4-triazole-3-thione (1e). A
mixture of benzoic hydrazide (0.45 g, 3.3 mmol)
and benzyl isothiocyanate (0.5 g, 3.3 mmol) was re-
fluxed in ethanol (50 ml) for 4 h to afford the cor-
responding thiosemicarbazide (0.8 g, 86%) as per
the reported procedure [3]. The separated thiosemi-
carbazide (0.78 g, 2.7 mmol) was refluxed in K2CO3
solution (60 ml, 10%) for 8 h, cooled, filtered, and
the filtrate washed with ether. The aqueous layer
was neutralized with cold dil. HCl. The separated
solid was filtered and washed with water to get
1e (0.6 g, 82%). The one-pot reaction used as in
the case of 1a–d gave 1e in less than 25% yield:
mp 278–280◦C (CHCl3); IR (KBr) 3087, 2931, 2752,
1506, 1353 cm−1; UV (MeOH) 258 nm; 1H NMR
(200 MHz, CDCl3)δ 5.34 (s, 2H, CH2), 7.11–7.55 (m,
10H, ArH), 12.47 (s, 1H, SH); 13C NMR (50 MHz,
CDCl3) δ 48.46 (CH2), 126.13, 127.49, 128.43, 129.18,
129.23, 129.40, 131.49, 135.55, 153.02 (C N), 169.06
(C S); 13C NMR-DEPT 135 (50 MHz, CDCl3) δ 43.46
(CH2), 125.49, 128.43, 129.18, 129.24, 129.41, 131.50,
4-(1-Naphthyl)-5-(o-tolyl)-1,2,4-triazole (2c). mp
164–166◦C (CHCl3); IR (KBr) 1598, 1487 cm−1; UV
1
(MeOH) 228, 282 nm; H NMR (400 MHz, CDCl3)δ
2.30 (s, 3H, CH3), 6.97–7.95 (m, 11H, ArH), 8.43
(s, 1H, CH); 13C NMR (50 MHz, DMSO-d6) δ 15.7
(CH3), 117.3, 121.2, 121.3, 121.8, 122.1, 122.9, 123.9,
124.3, 124.9, 125.6, 125.8, 126.1, 126.3, 129.4, 133.5,
141.5 (C3 CH), 149.2 (C N), 13C NMR-DEPT 135
(50 MHz, DMSO-d6) δ 15.7 (CH3), 117.3, 121.2, 121.3,