Ryan and O'Neill — Studies in the Diflavone Group. 171 



conditions mentioned above, condensed almost quantitatively with benzalde- 

 hyde to form benzylidene-3.4-dimethoxy-fiavanone (ix), and with anisaldehyde 

 to give the corresponding anisylidene-3. 4. 4'-trimethoxy-fiavauone (x). 



As piperonylidene-chalkones are only sparingly soluble in alcohol, the 

 condensation in the presence of hydrochloric acid of diacetoresorcinol and 

 piperonal gives mainly, even after addition of chloroform, in which the 

 chalkone is more soluble, piperonylidene-3. aceto-4. hydroxy-piperonylidene- 

 3'. 4'.-methylenedioxy-flavanone (vn). In the case of gallacetophenone- 

 dimethylether and piperonal in alcoholic hydrochloric acid the main product 

 is the chalkone, piperonylidene-gallacetophenone-dimethylether (xn), but at 

 the same time some piperonylidene-3. 4. dimethoxy-3'. 4'. methylenedioxy- 

 flavanone (xi) is formed. 



The diflavindogenide, dibenzylidene-diflavanone, has been already obtained 

 by Eijkman, Bergenia, and Henrard (loc. cit.) from a-dibenzylidene-diaceto- 

 resorcinol by condensation with benzaldehyde in a solution of anhydrous 

 hydrochloric acid in a mixture of alcohol and benzene. "We have also 

 utilized this method, which differs essentially from ours by requiring the 

 previous preparation of the dichalkone, for the preparation of dibenzylidene- 

 diflavanone, dianisylidene-diflavanone (xin).and dipiperonylidene-diflavanone 

 (xiv), and found it convenient for the purpose. 



Experimental Part. 



A. Isomeric Forms of Dibcnzylidene-diacetoresorcinol. 



1. Action of Aqueous Alkali on Diacetoresorcinol and Benzaldehyde. 

 We have shown (loc. cit.) that by shaking a solution of diacetoresorcinol 

 in dilute aqueous alkali with benzaldehyde, for about one month, a yellow 

 substance, which melts at 198-201° C, is formed. 



fi-Dibenzylidene-diacetoresorcinol. 



The substance consists of yellow crystals, which very closely resemble 

 cubes in appearance, but nevertheless are probably short monoclinic prisms, 

 the angles between the faces being very nearly right angles. The crystals 

 are doubly refractive, and have oblique extinction. 



In chloroform solution its diacetate reacted with bromine to form the 

 tetrabromide of dihydroxy-dichalkone-diacetate, which melted at 176-178° C, 

 and which was converted into diflavone by interaction with alcoholic potash. 

 Furthermore, as the same compound was produced by demethylating 

 dimethoxy-dichalkone by means of aluminium chloride, it must be dihydroxy- 

 dichalkone. 



