Synthesis And Wittig Olefination Of Cyclic ?-Alkoxyphosphonium Salts And Their Application In Synthesis Of Vinyl Ethers And Ketones

The Wittig reaction has become one of the important reactions to form carbon carbon double bond in organic synthesis. Vinyl ethers is a kind of organic compounds on the double bond of carbon containing alkoxy, they play a significant role in various of cycloaddition and other reactions and are found as constituent functional groups in bioactive products.In this paper, the discovery of in the reaction of 2-(diphenylphosphino)benzalcohol, aldehyde, with triphenylphosphine dibromide-vs.tetrafluoroborate allows entry to cyclic ?-alkoxyphosphonium salts. This reaction owns mild reaction conditions, simple operation, in addition, electron-deficient,electron-rich aromatic aldehydes and aliphatic aldehydes all can react in 36%- 89%yields. Cyclic ?- alkoxyphosphonium salt can react with a series of aromatic aldehydes to produce the corresponding vinyl ether in yield 45%-96%. The reaction conditions depend on the substrate aromatic aldehydes and aromatic aldehydes electron density on the aromatic ring used in the preparation of the phosphonium salt,for the phosphonium salt by the electron-deficient aromatic aldehydes prepared, they can react with various of aromatic aldehydes under the conditions of K2CO3 as base and DMSO / CH3CN(10/1) as the solvent; for the phosphonium salt from the electron-rich aldehyde prepared can react with electron-deficient aldehydes under the same conditions; but the reaction with electron-rich aldehydes needs t-BuOK made a base. The resulting vinyl ether can be hydrolyzed under refluxing for 30 min to the corresponding ketone in 6 M HCl / MeOH(3/1), thus providing a simple synthesis of1,2-diaryl ethanone route. This synthetic method has the following advantages:(1) A cyclic ?- alkoxy phosphine salt is very easy to get from 2-(diphenylphosphino)benzyl alcohol, and it is air stable solid good;(2) The materials are two aromatic aldehydes, and there are various combinations, such as electron-deficient and electron-rich, electron-rich and electron-deficient;(3) mild reaction conditions do not need the strong base such BuLi and LDA.