Benzenesulfonic acid, 4-methyl-, compd. with pyridine (1:1) → tert-butyl N-methyl-N-(4-oxocyclohexyl)carbamate

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Reaction Steps

A solution of (3,3-dimethyl-1,5-dioxa-spiro[5,5]undec-9-yl)-methyl-carbamic acid tert-butyl ester (9.53 g, 27.2 mmol, 1.0 eq.) and PPTS (2.1 g, 0.3 eq.) in acetone-water (2:1, 500 mL) was heated at 80° C. for 18 h, cooled to room temperature and concentrated to remove acetone. The residual aqueous solution was diluted with NaHCO3 and extracted with 2×EtOAc. The combined organic layer was dried over Na2SO4, filtered and concentrated. The crude product was purified by chromatography (20% to 50% EtOAc/hexanes) to give methyl-(4-oxo-cyclohexyl)-carbamic acid tert-butyl ester as a white solid (5.38 g, 87%).

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