Research On Addition Reachtion Of Towards Imines Catalyzed By Organic Rare-Earth Complex

The traditional cross-coupling reaction as well as the C-H bond activation reaction is of an important way to construct C-X(X=C?O?N)bond.The traditional cross-coupling reaction includes Heck?Suzuki-Miyaura?Stillc and Sonogashiira reaction,etc.However,these reactions,in contrast with C-H functionality,require a step of halogenating for the raw material in advance.Therefore,the transition metal-catalyzed C-H functionality has been an important means for synthesizing complex molecules with scientific value via direct construction of C-C bond,C-N bond,and C-O bond.Pyridine derivatives are among the important structural basis in many natural products,drugs,ligands and functional materials.Although several synthetic methods have been developed so far,a process for synthesis of pyridine derivatives from sample pyridine via C-H activation and subsequent transformation became a most straightforward way with atom-and step economy and less waste.This method is according with the purpose of green synthesis.Recently,rare-earth complex was found that it could serve as a catalyst for C-H activation under ambient conditions with excellent selectivity and high yield of product.In the course of C-H activation using rare-earth catalyst,the process contains the formation of new Ln-C bond and its transformation,which is different from the process of oxidative addition and reduction elimination in transition metal-catalyzed C-H functionality.Therefore,rare-earth-catalyzed C-H functionality could complete some unique reaction that is difficult for transition metal catalyst.On the basis of the review of transition metal-catalyzed C-H addition towards C=X(X=O,N)bonds and previous work of our group in rare-earth-catalyzed C-H addition towards olefins,this paper developed a new method for catalytic pyridine C-H addition across imine by a organo-rare-earth complex featuring a phosphinoamide ligand.The specific content is as follows:(1)The eleven rare-earth alkyl complex were synthesized via acid-base reaction of Ln(CH2C6H4NMe2-o)3(Ln=Y,Sc,Lu,Gd,Sm,Dy,Er,Ho,Tm)with various phosphinoamine(4a,4b and 4c).Their molecule structures were characterized by 1H NMR,13C NMR,31P NMR and single crystal X-Ray diffraction.(2)The reaction conditions were optimized for ortho-C(sp2)-H addition of pyridine towards imine and the optimal conditions are:complex 4b-Gd(10 mol%),the additive NH(SiMe3)2(10 mol%)and additive NHBn2(10 mol%),in toluene,at 100?;(3)Under the optimal conditions,the method for catalytic ortho-C(sp2)-H addition towards imine was established.The various substrates including pyridine and imine are tested by rare-earth catalyst,and found the complex 4b-Gd was compatible for these reaction with 28-81%yields of product.