Substituent Effects and Structural Limitations in the Conversion of 3,3-Diarylphthalides to 4,4-Diaryl-3,4-dihydro-1 (2H)-phthalazinones

概要

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Heating of crystal violet lactone (CVL) (1a) and its analogs with hydrazine hydrate afforded a single product in each case, to which the 4,4-diaryl-3,4-dihydro-1 (2H)-phthalazinone structure (2) was assigned. Kinetic data showed that the introduction of a dimethylamino substituent in 3,3-diarylphthalides (1) led to an increase in the rate of formation of the dihydrophthalazinone (2). Thus, the reaction seems to occur by a mechanism which involves a carbonium intermediate. Replacement of 3,3-diaryl groups on the phthalide by a xanthyl group resulted in the formation of an N-aminophthalimidine derivative on similar treatment. The dihydrophthalazinone (2a) exhibited a greenish-blue color on exposure to a weak acid, indicative of heterolytic ring cleavage to form the dye cation, whereas treatment of 2a with a strong acid resulted in a facile conversion to the N-aminophthalimidine (6) and CVL (1a) in a ratio of ca. 2 : 1.
公益社団法人日本薬学会の論文
1980-12-25