2-[6-(2-Hydroxyphenyl)-1,2,4,5-tetrazin-3-yl]phenol

Hydrazine hydrate (99%, 5g, 100 mmol) was added to a solution of 2-cyanophenol (2 g, 16.8 mmol) in absolute ethanol (30 ml) under N₂ atmosphere, and the reaction mixture was refluxed for 12 h. During the course of the reaction, the color of the solution changed to yellow, and the yellow precipitate, 2-[6-(2-hydroxyphenyl)-1,4-dihydro-1,2,4,5-tetrazin-3-yl]phenol, produced was readily oxidized in air to 2-[6-(2-hydroxyphenyl)-1,2,4,5- tetrazin-3-yl]phenol (0.9 g, 40% yield ), deep red crystals obtained from recrystallization from tetrahydrofuran.

¹H-NMR (300MHz, CDCl₃, δ_ppm, J_Hz): 10.88 (2H, s), 8.66 (2H, d, J=8.1), 7.55 (2H, dd, J=7.2, 5.2), 7.16 (2H, d, J=7.2), 7.13 (2H, dd, J=8.2, 5.2).

IR (KBr, cm^-1): 523 (m), 560 (w), 590 (w), 681 (s), 713 (s), 744 (s), 838 (m), 875 (w), 948 (m), 1029 (w), 1050 (m), 1094 (m), 1127 (w), 1155 (m), 1233 (s), 1273 (w), 1331 (w), 1386 (s), 1418 (s), 1472 (m), 1485 (s), 1577 (s), 1616 (s), 3119 (m).

UV-Vis (in CH₃CN): 295 (e = 2.14 x 104 mol^-1cm^-1), 355 (e = 1.86 x 104 mol^-1cm^-1) and 534 nm (ε = 3.96 x 102 mol^-1cm^-1).

FAB-MS [M+]: 266.

Calcd: C, 63.15; H, 3.79; N, 21.04 %. Found: C, 63.0; H, 3.8; N, 21.1 %.