Benzylhydrazine dihydrochloride → 1-benzyl-6-bromo-3-ethyl-1H-indazole

Participants

Reaction Conditions

Reaction Steps

Methanesulfonic acid 5-bromo-2-propionyl-phenyl ester (5.00 g, 16.3 mmol) was combined with benzylhydrazine dihydrochloride (4.45 g, 22.8 mmol) and sodium acetate (4.01 g, 48.9 mmol) in xylenes (30 mL). The reaction mixture was heated to 135° C. for two days using a Dean Stark apparatus. The reaction was cooled to room temperature, diluted with dichloromethane (75 mL), and washed with water (75 mL) and 1N aqueous hydrochloric acid (75 mL). The organic extracts were dried over magnesium sulfate and concentrated. The crude product was purified by chromatography on silica gel eluting with 4:1 hexanes/ethyl acetate to yield 2.10 g of 6-bromo-1-benzyl-3ethyl-1H-indazole (41% yield). 1H NMR (400 MHz, CDCl3) δ 1.39 (t, 3, J=7.7), 2.96 (q, 2, J=7.7), 5.48 (s, 2), 7.14-7.23 (m, 3), 7.26-7.31 (m, 3), 7.42 (s, 1), 7.54 (d, 1, J=8.5). 13C NMR (100 MHz, CDCl3) δ 13.70, 20.37, 52.68, 112.12, 120.77, 121.69, 121.83, 123.34, 126.97, 127.76, 128.75, 136.74, 141.37, 147.60. IR 3064, 3031, 2970, 2934, 2875, 1606, 1504, 1497, 1454, 1236, 1048, 831, 701 cm1. Analysis calculated for C16H15BrN2 : C, 60.97; H, 4.80; N, 8.89. Found: C, 61.21; H, 4.92; N, 8.73.

Provenance & Evidence