Whereas by the reaction of the formylation reagent, prepared from dimethylformamide and phosphorus oxychloride, with 1, 4-and I, 3-benzene diacetic acids the salts Ib and Ic were prepared, containing two trimethinium systems, with I, 2-benzene diacetic acid a cyclization reaction was observed, yielding the diformylindene derivative IlIa in low yield. In the course of the preparation of standard samples the formylation of indene by reagents of the ...
