Phthalide-3-carboxylic acid has been decarboxylated in the presence of isoquinoline, 1-chloroisoquinoline and isoquinoline N-oxides to give low yields of compounds resulting from alkylation of the isoquinoline heterocycle at C1 with a phthalidyl group. Attempted Barton decarboxylation-alkylation in the presence of isoquinolinium salts was unsuccessful.
The reactions of isoquinoline and phthalazine Reissert compounds with phthalaldehydic acids and their derivatives have been investigated as a means of synthesizing 1-(3-phthalidyl)isoquinolines. Of a variety of conditions tried those involving phase transfer were found, in general, to be the most suitable. The products, which are analogues of the convulsant alkaloid bicuculline, showed weak central nervous system depressant activity.
The lithiation of methoxy- and methylenedioxy-bemyl alcohols is described; subsequent reactions with ethyl chloroformate and carbon dioxide to form phthalides have been investigated, and are compared with metallation-carboxylation of alternative substrates. The preparation of phthalideisoquinoline analogues by this method proceeds only in low yields due to the acidity of the benzylic position in the benzylisoquinoline precursor.