p-Toluenesulfonic acid → 2-[(3aS,4R,7aR)-2,2-dimethylhexahydro-1,3-benzodioxol-4-yl]-1H-isoindole-1,3(2H)-dione

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Reaction Steps

To a solution of 2-[(1R,2S,3R)-2,3-dihydroxycyclohexyl]-1H-isoindole-1,3(2H)-dione (19) (50.0 g, 191.4 mmol) and 2,2-methoxypropane (500 mL, 4.07 mol) in acetone (500 mL), a catalytic amount of p-toluenesulfonic acid was added and the resulting reaction mixture was stirred at room temperature for 3 h. The reaction was quenched with saturated Na2CO3 solution to adjust the pH to 10 and the solvent was removed. Water (750 mL) was added to the residue and extracted with ethyl acetate (2×750, 500 mL). The organics were combined, dried over Na2SO4 and concentrated to give the desired product as a white solid (55.8 g, 96.8% yield). LC/MS [Method B: rt: 6.16 min; m/z: 302 (M+1)].

Provenance & Evidence