condensation of homophthalic anhydride.In the study of the interaction of homophthalic anhydride and methyl (triphenylphosphoranylidene)-acetate, along with (1-oxo-1H-isochromen-3-yl)acetate obtaining, two minor products -(1,3-dioxo-1,2,3,4-tetrahydronaphthalene-2-yl)acetate and 2-((1-oxo-1H-isochromen-3-yl)methyl)benzoic acid -had been isolated. The action of tert-butyl (triphenylphosphoranylidene)acetate on homophthalic anhydride didn't lead to Wittig reaction; the encumbered ylide demonstrated only its basicity, and products of homophthalic anhydride self-condensation -2-((1-oxo-1H-isochromen-3-yl)methyl)-benzoic acid and 12-hydroxy-5H-dibenzo[c,g]chromen-5-one -were formed. ________________________________________________________________________________