3-Cyanopyridine → 3-(3,5-Dibromobenzoyl)pyridine

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Reaction Conditions

Reaction Steps

A 2.5M solution of n-butyllithium in hexane (40.0 ml) was added dropwise to a stirred mixture of 1,3,5-tribromobenzene (31.5 g) and dry ether (1000 ml) at -78° C. under an atmosphere of dry nitrogen. The resulting solution was stirred at -78° C. for 30 minutes and then a solution of 3-cyanopyridine (10.4 g) in dry ether (100 ml) was added dropwise. The mixture was stirred at -78° C. for 1 hour and then the temperature was allowed to reach 0° C. 2N Hydrochloric acid (200 ml) was added, with stirring, and the ether layer was decanted off and then extracted several times with 2N hydrochloric acid. The acidic extracts were combined and warmed on a steam bath for 20 minutes, then the solution was cooled and basified with aqueous potassium hydroxide solution. The resulting solid was filtered off, washed with water, dried and combined with the solid obtained by evaporation under vacuum of the ether solution. The crude product was chromatographed on silica gel using dichloromethane as eluent; the earlier fractions contained impurity and the later fractions were combined and evaporated under vacuum. The solid obtained from the latter fractions was crystallised from ethyl acetate-hexane to give the title compound (23.33 g), m.p. 124°-126° C. Found: C, 42.50; H, 2.23; N, 4.21. C12H7Br2NO requires C, 42.26; H, 2.07; N, 4.11%.

Provenance & Evidence