A novel bismethylene transfer to 2′-hydroxylated isoflavones by dimethylsulphoxonium methylide: study of the reaction and its products

Abstract

Isoderritol isoflavone (IIa) reacts in a novel way with excess dimethylsulphoxonium methylide to yield the cyclopentene type (VIIa).

There is evidence for the intermediacy of the vinylcoumaranone (IV) and structural and mechanistic information is obtained by use of deuteriated ylide. Reactions of the product (VIIa) are studied. Under acid conditions it rearranges to the stilbenoid cyclopentenone (XVa) Whilst the dihydro-derivative (IXa) gives the hexacyclic product (XIa): mechanistic rationalisation is discussed. Derritol isoflavone undergoes similar reactions with the ylide.

A side-product in the isoderritol isoflavone reaction is decarboxyisorotenonic acid (VI) and it is shown that the isomerisation can be effected by sodium hydride–dimethyl sulphoxide.