The reactions of 2,2‐difluoro‐4‐methylnaphtho[l,2‐e]‐1,3,2‐dioxaborin and its [2,1‐e]isomer with N,N‐dimethylformamide

The title compounds react with dimethylformamide in acetic anhydride to give dimethylamino‐vinyl derivatives which, on treatment with base, yield benzochroman‐4‐ones. The [1,2‐e] isomer reacts with the Vilsmeier complex to give 3‐formylbenzo[f]chrom‐4‐one and 9‐hydroxy‐1‐phenalenone, and the [2,1‐e]isomer gives 3‐formylbenzo[h]chrom‐4‐one.