Methyl 3-oxo-3,4-dihydro-2H-1,4-benzothiazine-6-carboxylate → methyl 3,4-dihydro-2H-1,4-benzothiazine-6-carboxylate

Borane-tetrahydrofuran complex solution (1 M in tetrahydrofuran, 45 mL, 45 mmol) was added at 0° C. to a suspension of methyl-3-oxo-3,4-dihydro-2H-1,4-benzothiazine-6-carboxylate (2.00 g, 8.96 mmol) in tetrahydrofuran (20 mL). The ice bath was removed, the homogenous solution stirred at room temperature for 2 h, then excess reagent was destroyed by careful addition of methanol (42 mL) at 0° C. After evaporation of volatile material, the residue was taken up in 5% methanolic sulfuric acid solution (25 mL) and the solution was heated at reflux over 80 min. After cooling, the reaction mixture was partitioned between ethyl acetate and water, the organic layer was dried (MgSO4) and evaporated to produce 3,4-dihydro-2H-benzo[1,4]thiazine-6-carboxylic acid methyl ester (1.79 g, 96%). Light yellow solid, MS (ISP)=210.1 (M+H)+.

1. customThe ice bath was removed
2. customexcess reagent was destroyed by careful addition of methanol (42 mL) at 0° C
3. customAfter evaporation of volatile material
4. temperaturethe solution was heated
5. temperatureat reflux over 80 min
6. temperatureAfter cooling
7. customthe reaction mixture was partitioned between ethyl acetate and water
8. dry with materialthe organic layer was dried (MgSO4)
9. customevaporated

ORD record

ord-1b4592677626440290f5d03e0eae5472

Source dataset

uspto-grants-2011_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US08030308B2