Isoindole 1-phenyl-, acetylation

Benzodiazepinones also undergo rearrangement to isoindoles when treated with acetic anhydride and pyridine (Py). The diazepinone (81), for instance, gives l-phenyl-3-acetylisoindole (82) under these conditions. The structure of the product was established in this case by comparison with (82) prepared by acetylation of 1-phenyl-isoindole. The rearrangement may be formally represented by a... 

The acetylation of carbazole by acetic anhydride in the presence of boron trifluoride produces the 9-acetyl derivative. Further acetylation requires more vigorous conditions, using aluminum trichloride as a catalyst, and yields 2,9-diacetylcarbazole, which, upon base-catalyzed hydrolysis, produces 2-acetylcarbazole (80T3017). Acetylation of 1-phenyl-isoindole under mild conditions in the presence of pyridine yields l-acetyl-3-phenylisoin-dole, whereas the presence of an ester group at the 1-position deactivates the ring sufficiently to prevent acylation (81AHC(29)34l). 

Ethyl d,l-(a-Phthlalimidophenylacetyl) acetoacetate refluxed 14 hrs. in pyridine until COg-evolution ceases l-acetyl-3-phenyl-2,5(3H)-dioxo-5H-pyrrolo[2,l-a]-isoindole. Y 80-83%. F. e. s. K. Adank et al., Helv. 44, 2131 (1961). 

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