Sulfuric Acid → 2,5-Dihydro-5-phenyl-3H-imidazo(2,1-a)isoindol-5-ol

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Reaction Steps

Seventeen grams of the phthalimidine hydrochloride from above, 20 g. of p-butoxyphenylsulfonyl chloride and 200 ml. of pyridine are refluxed for two hours and then the mixture is evaporated to dryness. On recrystallization of the residue from ethanol there is obtained 9b-phenyl-1,2,3,9b-tetrahydro-1-(p-butoxyphenylsulfonyl)-1H-imidazo [2,1-a]isoindol-5-one which is admixed with 25 ml. of 95 percent sulfuric acid for one hour. The reaction mixture which contains the sulfate salt of 2-(2-imidazolin-2-yl) benzophenone is then cooled by the addition of ice water and made alkaline by the addition of a 5N potassium hydroxide solution. The product is then separated by filtration and recrystallized from dioxan to afford 2,3-dihydro-5-phenyl-5H-imidazo[2,1-a]isoindol-5-ol, m.p. 207 C., as a white crystalline solid which is insoluble in water and soluble in dimethylacetamide and ethanol.

Provenance & Evidence