Based On The Transformational Research Of Enynals And Alkenes

Enynals is the one of the universal and high-efficiency synthons, which has been widely used to synthesize cyclic compounds by synthetic chemists recently due to its unique property when catalyzed by metal. Based on the fundamental study of acetylene carbonyl compounds conducted by our group and the current research background of acetylene carbonyl compounds, we aimed to systematically study and explore metal-catalyzed Diels–Alder reactions of enynals and unsaturated hydrocarbon.This article is mainly divided into the following two parts: 1) Research of Metal-catalyzed Diels–Alder reaction of enynals with olefinsDue to the likely rearrangement of the double bonds and difficulties in isolation from the isomers of cyclohexadiene(CHD), it would be a great challenge to selectively and efficiently synthetize 1,3-CHD and its isomers in organic chemistry. Therefore, we developed an efficient and practical method for the synthesis of the isomers of CHD via indium or copper-catalyzed reaction of enynal with alkenes. Mechanically speaking, the intermediate pyrylium A was generated in situ from the subsequent nucleophilic attack of the carbonyl oxygen atom to the electrondeficient alkyne, A Diels–Alder reaction between pyrylium A and alkene was followed to furnish the intermediate B. From the intermediate B, two different ways occurred. The breaking of the C–O bond could lead to the allyl cation E′with C–M being intact( path b, M = [Au] or In Cl3) or the enolate allyl cation E( path a, M = Cu(OTf)2). β-Deprotonation elimination of E or demetalation of E′selectively afforded the isomers of 1,3-cyclohexadienes and 2,4-cyclohexadienes2)Research and exploration of metal-catalyzed reaction of linear azidoenynes with olefins or enynyl estersWe systematically investigated different metal catalysts for the reaction of linear azidoenynes with styrene. Experimental results showed that the relevant products could be afforded selectively when different metal salts were applied as catalysts. It can be indirectly indicated from one of the structure of product that the metal carbenoid indeed existed in the reaction system. Besides, we also found that halogen-substituted pentadienoic acid esters could be selectively formed in the reaction of enynyl esters catalyzed by Fe Cl3 and Fe Br3. Reaction conditions, such as temperature, solvent, were optimized systematically. We also furthered our study of chemical transformations of the product.