Triethylamine → 8-Tert-butyl-1-oxa-2-azaspiro[4.5]dec-2-ene-3-carboxylic acid ethyl ester

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Reaction Steps

A solution of 2-chloro-2-hydroxyiminoacetic acid ethyl ester (2.2 g, 14.6 mmol) in DCM (20 ml) was slowly added dropwise at 0° C. to a solution of 1-tert-butyl-4-methylenecyclohexane (740 mg, 4.86 mmol) in DCM (20 ml). Subsequently, a solution of triethylamine (1.5 ml) in DCM (10 ml) was slowly added dropwise at 0° C. and the resulting mixture was stirred overnight at RT. The reaction mixture was diluted with water. The aqueous phase was extracted several times with DMC. The combined organic phases were dried and the solvent was removed under vacuum. After purification of the residue (silica gel, hexane/ether 2:1) by column chromatography, the desired product 8-tert-butyl-1-oxa-2-azaspiro[4.5]dec-2-ene-3-carboxylic acid ethyl ester was obtained as a yellowish liquid (1.21 g, 93% of the theoretical amount).

Provenance & Evidence