Formamide → 2-Isopropyl-5-(2-nitro-phenylamino)-thiazole-4-carboxylic acid amide

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Reaction Steps

Stir 2-isopropyl-5-(2-nitro-phenylamino)-thiazole-4-carboxylic acid ethyl ester (68.6 g, 204 mmol) at rt under N2 as a slurry in DMF (205 mL). Add formamide (32.4 mL, 816 mmol, 4.0 eq.) in one portion, and heat the thick red slurry to 100° C.; a dark red/purple solution is formed. Add dropwise over 20–30 min, 25% NaOMe in MeOH (32.6 mL, 143 mmol, 0.7 eq.) Increase the temperature 120° C. and stir the dark solution was stirred at 120° C. overnight until complete (<2% Me ester+SM) by HPLC (Zorbax SB C18 25 cm, 60:40/ACN:0.1% TFA in water, 233 nm, 1.0 mL/min). After cooling the reaction to rt, add aqueous 5% NH4Cl (410 mL) at such a rate as to maintain the temperature below 35° C. with no external cooling. Precipitate the product, cool the slurry to 0–5° C., filter by vacuum filtration and dry in a vacuum oven at 60° C. to afford 52.7 g (84% yield) crude title compound as a purple solid that was used without further purification. An aqueous workup may result in bad emulsions/slow separations. 1H NMR (300 MHz, DMSO-d6) δ 12.22 (bs, 1H), 8.21 (d, 1H, J=7.69 Hz), 7.78 (m, 2H), 7.59 (bs, 1H), 7.53 (bs, 1H), 7.15 (m, 1H), 3.23 (dq, 1H, J=6.95 Hz), 1.35 (d, 6H, J=6.95 Hz). 13C NMR (75 MHz, DMSO-d6) δ 165.53, 161.44, 144.58, 137.12, 136.31, 135.72, 128.90, 126.58, 121.08, 116.28, 32.32, 22.35(2). IR (CHCl3) 3520, 3400, 3004, 2967, 2925, 2866, 1658, 1611, 1578, 1513, 1427, 1342 cm−1. HRMS(ES) M/z calculated for C13H14N4O3S1 329.0684, found 329.0667.

Provenance & Evidence