CYCLIC COMPOUNDS CONTAINING A CARBONYL GROUP; A MECHANISM FOR THE FORMATION OF PYRYLLIUM SALTS FROM 1,5-DIKETONES

Abstract

In the presence of alkali, cyclohexanone and its homologues add to chalcones to form either semicyclic diketones or dicyclic keto-alcohols; the latter contain a carbonyl bridge, and the former can be converted into closed ring structures and dehydrated to form substances having a carbonyl bridge. In these dicyclic ketones the bridge is not removed by heating, in contrast to the behavior of certain other compounds having a similar ring system.A second mode of ring closure gives rise to pyryllium salts; the isolation of a methyl ether has made it possible to devise a plausible mechanism for this hitherto obscure reaction. Four varieties of salts are described, the perchlorates being obtained by a different procedure than that previously employed.