Central nervous system active compounds. XII. The synthesis and properties of 3-dimethylaminomethylene phthalides

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Abstract
Isobenzofuran-l(3H)-one (phthalide), and its derivatives react with dimethylformamide dimethyl acetal to form 3-dimethylaminomethyleneisobenzofuran-1-one and minor amounts of the corresponding internal betaine 2-(2-carboxylatophenyl) ethynyltrimethylammonium. The use of t-butoxy- is(dimethylamino)methane allows the isolation of the corresponding aminal, which readily loses dimethylamine on recrystallization. The dimethylamino group in the title compounds is replaceable by amino, hydrazino or hydroxy groups in mildly acidic solution. 3-Formylphthalide, the tautomer of the last-named product, could be isolated as the 2,4-dinitrophenylhydrazone.