Hydrazine → 3-Benzyl-8-chloro-[1,2,4]triazolo[4,3-a]pyrazine

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Reaction Steps

2-Chloro-3-hydrazinopyrazine was prepared in four steps. The procedure of J. Adachi and N. Sato, J.Org.Chem. 37, 221 (1972) was used to prepare 2,3(1H,4H)-pyrazinedione in two steps, followed by chlorination and reaction of the dichloropyrazine with hydrazine as described in S. W. Schneller and J. L. May, J.Het.Chem. 15,987 (1978). A mixture of 2-chloro-3-hydrazinopyrazine (8.51 g, 58.9 mmol), 1-fluoro-2-(2,2,2-triethoxyethyl)benzene from 1(A) (34.7 g, 135 mmol) and xylene (125 mL) (dried over calcium chloride) was refluxed for 3 hours. The solvent was removed by spin evaporation in vacuo. The solid residue was triturated in ether (200 mL) and the solid was collected by suction filtration. The solid was rinsed with ether and dried with aspirator suction to give 14.9 g (96%) of crude 3-benzyl-8-chloro-1,2,4-triazolo[4,3-a]pyrazine. Recrystallisation of 1.0 g of crude 3-benzyl-8-chloro-1,2,4-triazolo[4,3-a]pyrazine from ethanol:water gave 0.697 g of the analytically pure product, mp. 126°-127° C.; UV (0.1 N hydrochloride acid+10% ethanol): λmax 300 nm (ε4200); (pH 7.0 buffer+10% ethanol): λmax 300 nm (ε4300); nmr(DMSO-d6) δ8.58 (d, 1H, J=4.7 Hz, H-5 or H-6), 7.79 (d, 1H, J=4.7 Hz, H-5 or H-6), 7.09-7.40 (complex multiplets, 4H, ArH), 4.60 (s, 2H, CH2); ms: m/e 262 (M+), 261 (M-1+), 243 (M-F+), 227 (M-Cl+), 109 (C7H6F+).

Provenance & Evidence