Abstract
A simple solvent-free protocol for the preparation of flunixin, a potent non-narcotic, non-steroidal anti-inflammatory drugs is reported using boric acid as catalyst. Its salt, flunixin meglumine are then prepared under reflux in EtOH. This sustainable method are then extended for the synthesis of a series of 2-(arylamino) nicotinic acid derivatives. The present protocol combines non-hazardous neat conditions with associated benefits like excellent yield, straightforward workup, and use of readily available and safe catalyst in the absence of any solvent, which are important factors in the pharmaceutical industry. The pathway for catalytic activation of 2-chloronicotic acid with boric acid was also investigated using Gaussian 03 program package.
Highlights
Flunixin, 2-(2-methyl-3-trifluoromethylanilino)nicotinic acid (Fig. 1) is a non-narcotic, non-steroidal anti-inflammatory drug (NSAID) and cyclooxygenase inhibitor with potent antipyretic and analgesic activity, parenterally administered in clinical and veterinary applications [1–3]
We have considered the synthesis of 2-(2-methyl-3-trifluoromethylanilino)nicotinic acid (3a), in the presence of boric acid under solvent-free conditions, and its salt, flunixin meglumine (6) under reflux in EtOH (Scheme 1)
The calculations overall indicate small affinity of boron for the nitrogen donor atom (IMB1) so that the optimized structure tend to form hydrogen bonds (HBDs) in (IMB 81) and give strong support to the suggested mechanism in which HBD formation between nitrogen in pyridine and OH of Boric acid is the preferred mode of activation
Summary
2-(2-methyl-3-trifluoromethylanilino)nicotinic acid (Fig. 1) is a non-narcotic, non-steroidal anti-inflammatory drug (NSAID) and cyclooxygenase inhibitor with potent antipyretic and analgesic activity, parenterally administered in clinical and veterinary applications [1–3]. 2-(2-methyl-3-trifluoromethylanilino)nicotinic acid (3a) under solvent-free conditions in the presence of catalytic amount of Boric acid. We have considered the synthesis of 2-(2-methyl-3-trifluoromethylanilino)nicotinic acid (3a), in the presence of boric acid under solvent-free conditions, and its salt, flunixin meglumine (6) under reflux in EtOH (Scheme 1).
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