Abstract
6-Methyl-5-hepten-2-one (MH), a useful intermediate for the synthesis of terpenes and vitamines, was prepared by aqueous-organic and solid organic two-phase reactions of NaOH or KOH, acetone, and 1-chloro-3-methyl-2-butene (prenyl chloride, PC). Quaternary ammonium and phosphonium halides were used as phase-transfer catalysts in aqueous NaOH-organic two-phase reactions ; among these, tetra-n-butylammonium bromide was found to be the most effective catalyst. The yield of MH depended mainly on the structure of the catalyst, acetone/PC and NaOH/PC ratio, and the best yield was 52%. 18-Crown-6 and dibenzo-18-crown-6 were found to promote solid KOH-organic two-phase reactions, but were ineffective in aqueous KOH-organic reaction.
