Carbon Dioxide → 4-((tert-Butoxycarbonyl)amino)-3-methylisothiazole-5-carboxylic acid

Participants

Reaction Steps

To a solution of (3-methyl-isothiazol-4-yl)-carbamic acid tert-butyl ester (method 55) (21.4 g, 100 mmol) in anhydrous THF (200 mL) at -78° C., LDA (139 mL, 1.8 M solution, 250 mmol) was added dropwise over a period of 1 h. The reaction mixture was stirred at that temperature for a further 3 h after which powdered dry ice was added and the reaction slowly allowed to warm to room temperature overnight. The reaction mixture was quenched by adding saturated NH4Cl solution and extracted with ether (3×100 mL) and the combined ether layers were back extracted with satd. NaHCO3 (3×100 mL). The aqueous layers were combined and acidified to pH 5 using 6M HCl and extracted with ether (4×100 mL). The combined ether layers were dried (Na2CO3) and concentrated to give the pure acid as an off white powder. Yield 11 g (39%). 1H NMR (300 MHz) δ 1.47 (s, 9H), 2.44 (s, 3H), 8.53 (bs, 1H), 9.68 (bs, 1H).

Provenance & Evidence