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b2003030181(金币+50, 翻译EPI+1): 2010-04-10 14:55
sirljz(金币+3):谢谢交流，欢迎常来 2010-04-10 15:16
the synthesis of alkenes by Hydrogenolysis of allylic compounds is a simple reaction with wide synthetic application.The reaction has advantages due to its regio- and stereoselective process, especially in the filed of the synthesis of natural products and mediine. In the past decades, most researches were concentrated on the palladium-catalyzed hydrogenolysis of allylic compounds and its synthetic applications. Only limited reports about other metal-catalyzed this type of reaction could be found.
The purpose of the study was to select the cheap metal, copper and used Cu-H, to catalyze the hydrogenolysis of allylic compounds. The thesis reported the preparation of some allylic ester compounds, and the effects of different substrates under optimal reaction conditions. A series of cumulated diolefins were obtained and the catalytic system of substrate scopes was found. The best catalytic condition was OCO2iPr as leaving group, CuOtBu as cooper salt, catalyst 5 %,toluene/ PMHS（4eq.） as reductive system and room temperature,with 83.9 % yied and high regioselective ratio of 96:1:3.When the phosphoric ester was leaving group,the yied was 91% with high regioselective ratio was 93 : 3 : 4.
The reaction mechanism and the reaction process mechanism were summarized to compare copper-catalyzetion with palladium-catalyzetion. It is well-known that various allylic compounds undergo facile palladium-catalyzed transformations via Π-allylpalladium complex as an intermediate. But, the current study indicated that copper-catalyzed system may have different mechanisms from palladium-catalyzed system,which undergoes reductive elimination via the σ-allylcooper, and H-attace theγ-C, resulting the transferring of the hydride to the less substituted side of the allylic system. |
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