Phthalic Anhydride → 2-(3-(Tert-butoxycarbonyl)phenyl)-3-methylpyridine 1-oxide

Participants

Reaction Conditions

Reaction Steps

tert-Butyl-3-(3-methylpyridin-2-yl)benzoate (1.0 eq) is dissolved in EtOAc (6 vol). Water (0.3 vol) is added followed by urea-hydrogen peroxide (3 eq). The phthalic anhydride (3 eq) is added portion-wise as a solid to maintain the temperature in the reactor below 45° C. After completion of phthalic anhydride addition, the mixture is heated to 45° C. After stirring for an additional 4 hours, the heat is turned off 10% w/w aqueous Na2SO3 (1.5 eq) is added via addition funnel. After completion of Na2SO3 addition, the mixture is stirred for an additional 30 minutes and the layers separated. The organic layer is stirred and 10% w/w aq. Na2CO3 (2 eq) is added. After stirring for 30 minutes, the layers are allowed to separate. The organic phase is washed 13% w/v aq NaCl. The organic phase is then filtered and concentrated to afford crude 2-(3-(tert-butoxycarbonyl)phenyl)-3-methylpyridine-1-oxide (95%) that is used directly in the next step.

Provenance & Evidence