2,6-Difluorobenzoic acid → 2,6-Difluorobenzoyl chloride

Participants

Reaction Steps

A mixture of 2,6-difluorobenzoic acid (10 g, 63.3 mmol) and DMF (3 drops) in dichloromethane (150 ml) was treated with thionyl chloride (23 ml, 316.5 mmol). The mixture was heated at reflux overnight. The solvent was removed in vacuo and the residue azeotroped (toluene 3×50 ml) to give 2,6-difluorobenzoyl chloride as an oil (8.59 g, 77%). N Boc-L4-aminophenylalanine methyl ester (100.92 g, 40.6 mmol) and NMM (5.3 ml, 48.7 mmol) were added to a solution of the above acid chloride in DMF (50 nm). The mixture was stirred at room temperature for 2 h. The solvent was removed in vacuo and the residue partitioned between ethyl acetate and aqueous. The aqueous layer was extracted with ethyl acetate (3×100 ml). The combined organic layers were dried (MgSO4) and evaporated in vacuo to give a pale brown oily solid. Trituration with ether gave the title compound as a white solid (6.93 g). δH(d6 DMSO) 7.67-7.53 (3H, m), 7.27-7.20 (5H, m), 4.19-4.11 (1H, m), 3.62 (3H, s), 3.00-2.73 (2H, m), 1.33 (9H, s); m/z (ESI, 70V) 457 (M++Na).

Provenance & Evidence