2,2-Dimethoxypropane → Tert-butyl 6'-bromo-2,2-dimethyl-2'-oxospiro[[1,3]dioxane-5,3'-indoline]-1'-carboxylate

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Reaction Steps

To a solution or tert-butyl 6-bromo-3,3-bis(hydroxymethyl)-2-oxoindoline-1-carboxylate (1.00 g, 2.69 mmol) and 4-methylbenzenesulfonic acid hydrate (0.026 g, 0.134 mmol) in DMF (27 mL) was added 2,2-dimethoxypropane (0.49 mL, 4.03 mmol). The solution was stirred at rt overnight followed by the addition of additional 2,2-dimethoxypropane (0.49 mL, 4.03 mmol) and 4-methylbenzenesulfonic acid hydrate (0.026 g, 0.134 mmol). After stirring at 60° C. for 5 h, the solution was poured into saturated aqueous NaHCO3 and extracted with DCM. The combined organic extracts were purified by column chromatography (eluting with a gradient of 0-30% EtOAc in hexanes) to give tert-butyl 6′-bromo-2,2-dimethyl-2′-oxospiro[[1,3]dioxane-5,3′-indoline]-1′-carboxylate as a white solid. Mass Spectrum (ESI) m/e=434.0 [(M+Na+) (79Br)] and 436.0 [(M+Na+) (81Br)].

Provenance & Evidence