Lithium Hydroxide → 3-Oxo-3,4-dihydro-2H-1,4-benzothiazine-6-carbaldehyde

Participants

Reaction Steps

3-Oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carboxylic acid. To a solution of 3-oxo-3,4-dihydro-2H-benzo[1,4]thiazine-6-carboxylic acid methyl ester (1.5 g, 6.7 mmol) in a THF/H2O mixture (1:1, 63 mL) was added 4 N LiOH (8.0 mL, 32 mmol) and the resulting solution was stirred at RT for 24 h. The solution was partially concentrated and diluted with H2O (50 mL). The solution was acidified using concentrated HCl and a solid precipitated. The solid was collected via filtration, washed with H2O and dried in vacuo to provide 0.79 g (60%) of the title compound as a white solid. MS (ESI): exact mass calculated for C9H7NO3S, 209.01; m/z found, 210.2 [M+H]+. 1H NMR (500 MHz, CD3OD): 7.65-7.61 (m, 2H), 7.40 (d, J=8.1, 1H), 3.48 (s, 2H).

Provenance & Evidence