Dimethylformamide → 4-Allyloxycarbonyl-2-nitrobenzoic acid

Participants

Reaction Steps

Nitroterephthalic acid (6.33 g) in methylene chloride (75 ml) and THF (15 ml) was converted to the mono acid chloride using oxalyl chloride (2.63 ml), DMF (2.55 ml) and N-methylmorpholine (7.95 ml) at −10° C. After 1 hour the solvents were removed and, without further purification, the product was dissolved in allyl alcohol (20 ml) and THF (10 ml) and stirred overnight at ambient temperature. The solvents were removed and the residue partitioned between EtOAc and aqueous NaHCO3. Acidification of the NaHCO3 solution and extraction with EtOAc gave the product, 4-allyloxycarbonyl-2-nitrobenzoic acid (6.8 g). Nmr (CDCl3): δ 4.89 (d, 2H); 5.31-5.49 (m, 2H); 5.95-6.15 (m, 1H); 7.94 (d, 1H); 8.36 (dd, 1H); 8.54 (d, 1H). Without purification, this acid was converted by the method above to the acid chloride which was dissolved in THF (100 ml) at 0° C. Ammonia gas was bubbled into the solution until the reaction was completed. The solution was partitioned between EtOAc and water, and the product from the organic fraction purified on silica, eluting with methylene chloride followed by EtOAc. The product (4 g), containing a small impurity, was reduced with SnCl2 by a similar method to that in example 12 giving 4-allyloxycarbonyl-2-aminobenzamide. Nmr (DMSO-d6): δ 4.79 (d, 2H); 5.22-5.46 (m, 2H); 5.91-6.13 (m, 1H); 7.02 (dd. 1H); 7.37 (d, 1H); 7.61 (d, 1H). (2S,4S)-4-Acetylthio-1-(4-nitrobenzyloxycarbonyl)-2-carboxy-pyrrolidine (1.58 g) was converted to the acid chloride by suspension in methylene chloride (25 ml) and addition of oxalyl chloride (1.52 ml). A few drops of DMF were added. After 2 hours the solvents were evaporated and the acid chloride, dissolved in methylene chloride (10 ml), was added under argon to a solution of 4-allyloxycarbonyl-2-amino-benzamide (0.52 g) in THF (10 ml) and methylene chloride (5 ml) containing N-methylmorpholine (0.38 ml) at 0° C. The reaction was left overnight and partitioned between methylene chloride and dilute aqueous HCl. The methylene chloride fraction was washed with water, brine and dried. Purification was by silica chromatography, eluting with increasing concentrations of EtOAc in methylene chloride, giving (2S,4S)-4-acetylthio-1-(4-nitrobenzyloxycarbonyl)-2-(3-allyloxy-carbonyl-6-carbamoylphenylcarbamoyl)pyrrolidine (0.84 g). Nmr (CDCl3): δ 2.25 (quintet, 1H);.2.29 (s, 3H); 2.83 (m, 1H); 3.53 (dd, 1H); 4.02 (quintet, 1H); 4.2 (dd, 1H); 4.49 (dd, 1H); 4.85 (d, 2H); 5.23-5.46 (m, 2H); 5.97-6.13 (m, 1H); 7.31-7.5 (broad, 2H); 7.57 (d, 1H); 7.75 (dd, 1H); 7.81-7.95 (broad, 2H); 9.27 (d, 1H).

Provenance & Evidence