Sodium Bicarbonate → Tert-butyl 4-hydroxy-6-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)spiro[chroman-2,4'-piperidine]-1'-carboxylate

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Reaction Steps

To a solution of 13.4 g of tert-butyl 4-{[tert-butyl(dimethyl)silyl]oxy}-6-(5-oxo-4,5-dihydro-1,2,4-oxadiazol-3-yl)spiro[chroman-2,4′-piperidine]-1′-carboxylate in 200 mL of EtOH-THF (5.5:1) at 0° C. was added 67 ml of 1M HClaq dropwise, and the reaction mixture was stirred at r.t. for 18 h. The reaction mixture was cooled to 0° C., and the mixture was basified with NaHCO3. The mixture was concentrated in reduced pressure, and the residue was acidified with 1M HClaq. The aqueous mixture was extracted with a mixture of CHCl3-MeOH (9:1) three times, and the combined organic layers was washed with brine, dried over Na2SO4, and concentrated in reduces pressure to give the product as a pale brown solid.

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