If the ketone I1 does exist in part as the cyclic structure XV, it follows that 11, as well as IV, should give the chroman XVI with sulfuric acid. This was in fact the case; when boiled with 60% sulfuric acid, I1 gave XVI in 20% yield. These reactions involved not only hydrolysis and decarboxylation, but reduction or disproportionation as well. The best yield of XVI obtained was 28%(from IV), and while John and Giinther8 obtained much better yields of ...
