Cyclohexanecarboxaldehyde → 2-[(tert-butyl-dimethyl-silanyloxy)-cyclohexyl-methyl]-3-methyl-5-oxo-2,5-dihydro-1H-pyrrole-2-carboxylic acid methyl ester

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Reaction Steps

tert-Butyldimethylsilyltrifluoromethanesulfonate (2.40 ml, 2.75 g, 10.4 mmol, 2.0 equiv) was added dropwise over 8 min to a stirring solution of 5-(tert-butyl-dimethyl-silanyloxy)-3-methyl-1H-pyrrole-2-carboxylic acid methyl ester (1.4 g, 5.2 mmol, 1.0 equiv) and cyclohexanecarbaldehyde (0.94 ml, 0.87 g, 7.8 mmol, 1.5 equiv) in dichloromethane (100 ml) at −78° C. The resultant solution was stirred at −78° C. for 2 h, then pH=7 buffer solution (50 ml) was added. The organic layer was washed with brine solution (50 ml), and dried over sodium sulfate. The solids were filtered and the filtrate was concentrated. The residue obtained was purified by flash column chromatography (5% ethyl acetate-dichloromethane initially, grading to 8% ethyl acetate-dichloromethane, then to 10% ethyl acetate-dichloromethane) to give 2-[(tert-butyl-dimethyl-silanyloxy)-cyclohexyl-methyl]-3-methyl-5-oxo-2,5-dihydro-1H-pyrrole-2-carboxylic acid methyl ester (1.69 g, 85%) as a colorless oil.

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