Thiochroman-4-one → Methyl 4-oxothiochromane-3-carboxylate

Participants

Reaction Conditions

Reaction Steps

LHMDS (1.12 g, 6.7 mmol) dissolved in anhydrous THF (7 ml) was cooled to −78° C. under N2. Thiochroman-4-one (1.00 g, 6.1 mmol) in anhydrous THF (20 ml) was added dropwise under 20 minutes. After an additional 60 minutes methyl cyanoformate (0.62 g, 7.3 mmol) in anhydrous THF (1.5 ml) was added dropwise under 5 minutes and the suspension was then stirred at −78° C. for 80 minutes. The suspension was poured onto 10% NH4Cl and extracted with ether. The organic phase was washed with water, dried (Na2SO4), filtered and the solvent evaporated. The crude product was purified by chromatography on silica gel (heptane-ethyl acetate 10:1) to yield 4-oxo-thiochroman-3-carboxylic acid methyl ester (0.65 g): 1H NMR (400 MHz, CDCl3; enol tautomer) δ 12.64 (1H, s), 7.83 (1H, d), 7.25-7.29 (2H, m), 7.16-7.20 (1H, m), 3.84 (3H, s), 3.71 (2H, s).

Provenance & Evidence