5-Thiazolecarboxylic acid, 2-methyl- → 2-[2-(3-Butyl-5-methyl-isoxazol-4-yl)-2-hydroxy-ethyl]-thiazole-5-carboxylic acid methyl ester

Participants

Reaction Steps

To a stirred solution of 2-methyl-thiazole-5-carboxylic acid (215 mg, 1.50 mmol) in THF (10 mL) at −78° C. and under argon was added n-butyllithium (1.88 mL of a 1.60M solution in hexane, 3.0 mmol) dropwise. After 1 h, a solution of 3-butyl-5-methyl-isoxazole-4-carbaldehyde (251 mg, 1.50 mmol) in THF (10 mL) was added dropwise. After 2 h the reaction mixture was quenched with 10% aqueous citric acid (10 mL) then warmed to room temperature. The reaction mixture was extracted with ethyl acetate then the combined extracts were dried, filtered and concentrated. The resultant oil was redissolved in methanol (15 mL) and ether (7 mL) then (trimethylsilyl)diazomethane (2.25 mL of a 2M solution in ether, 4.5 mmol) was added dropwise. After 30 min, further (trimethylsilyl)diazomethane (2.25 mL of a 2M solution in ether, 4.5 mmol) was added. After 30 min, the reaction mixture was quenched with acetic acid (3 drops) then was concentrated and the residue redissolved in ethyl acetate and washed with NaOH (2 N). The organic phase was dried, filtered and concentrated then purified by chromatography (silica, 0 to 4% methanol in dichloromethane) to give the title compound (49 mg, 10%) as a brown oil. MS: m/e=307.3 [M+H]+.

Provenance & Evidence