Dimethylallylation products of phloroacetophenone; a convenient one-stage synthesis of deoxyhumulones

Abstract

The structures of seven products of the reaction between 2-methylbut-3-en-2-ol and phloroacetophenone, catalysed by boron trifluoride–ether complex, are described; they include the important 2,4,6-trihydroxy-3,5-bis-(3-methylbut-2-enyl)acetophenone (4-deoxyacetohumulone). By a similar reaction the natural hop compounds 4-deoxyhumulone, 4-deoxycohumulone, and 4-deoxyadhumulone are readily synthesised. No 4-deoxyacetohumulone was obtained by reaction of 6-acetyl-2,2,8,8-tetramethyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-5-ol with lithium in liquid ammonia.