Synthesis Of Aliphatic Acyloin And Vic-Dione

Aliphatic acyloin and α-diketone are important food flavors which could bewidely used in candy, caramel and cigarette, etc. Meanwhile, they’re also importantintermediates in organic synthesis. In this article, we designed an atom-economicmethod to synthesize acyloin series, followed by green oxidation using hydrogenperoxide to synthesizeα-diketone.Acyloins were synthesized from two molecules of aliphatic aldehyde in thepresence of Na2CO3by using N-benzyl-5-(2-hydroxyethyl)-4-methyl-1,3-thiazoliumchlorinum as catalyst.Seft-coupling and cross-coupling products were obtained when two differentaldehydes were used.In order to get asymmetric α-diketone, we screened thecross-coupling condition and the optimized selectivity were give herein. In the presence of sulfuric acid, the iron cation could oxidize acyloin to α-diketone.The ferrous cation could be recycled in the reaction by the oxidation of hydrogenperoxide. The results were here attached.As the purification of the above reaction products would cause some problems, wedeveloped a method to obtain α-diketone from methyl acetoacetate. Methylacetoacetate was alkylated by alkyl halides in basic condition and then oximated togive oxime ketones，after which α-diketone was obtained by the oxime exchange withformaldehyde in acidic condition.