Fixation of the aromatic double bonds in the chromones

Abstract

7-Allyloxyflavone undergoes Claisen transformation to form 8-allyl-7-hydroxyflavone, the constitution of which is established from its synthesis from 3-allyl-resacetophenone. The bond distribution should therefore be as in (I). However 8-alkyl substituted derivatives undergo coupling with diazotised p-nitraniline to form dyes and 7-allyloxy-8-allylflavone undergoes further transformation to form 6: 8-diallyl-7-hydroxy-flavone. Closely analogous results are obtained from 2-methyl-3-methoxy-7-hydroxychromone. It is therefore concluded that though the chromones generally react in form (I) the alternative disposition of the bonds (IV) is not precluded.