Theoretical Study On The Mechanism Of Ni-Al Bimetallic Catalyzed Dual C-H Bond Cyclization

Transition metal catalyzed activation reactions have received continuously increasing attentions in recent years,among which the cyclization has already become a powerful tool in organic synthesis of many useful active natural products.The cyclization commonly relies on transition metal catalysts,such as gold,palladium,rhodium,nickel,etc.Among these transition metals,nickel plays a significant role in cyclization due to its low price,low toxicity and strong coordination characteristics.The synergistic combination of nickel catalyst with Lewis acid is generally suggested as a promising strategy to achieve the improved reaction efficiencies.In this dissertation,we studied Ni-Al bimetallic catalyzed cyclization of amides and internal alkynes theoretically.By using the density functional theory methods,the reaction mechanism and reaction characteristics have been revealed at the molecular level for deep understanding of this kind of cyclization reactions.It provides an important theoretical reference for the subsequent design of better synthetic pathways and the development of higher performance catalysts and new synthetic materials.The main innovations achieved in this dissertation are listed as follows:The reaction mechanism of Ni-Al bimetallic catalyzed dual C-H bond cyclization of amides and internal alkynes has been studied theoretically.Four reactions were considered with N-phenylformamide（S1）and（R,R）-N,N-bis（1-phenylethyl）formamide（S2）as amides,second phosphine oxide（SPO）and PMe₃ as ligands,respectively.For two reactions with SPO as ligand and the reaction of S2 with PMe₃,the reaction mechanism mainly includes formyl C（sp²）-H bond activation,phenyl C（sp²）-H or alkyl C（sp³）-H bond activation,release of alkene,alkyne coordination and insertion,isomerization,and reductive elimination steps generating the cyclization product.The reaction of S1 with PMe₃ proceeds via formyl C（sp²）-H bond activation,isomerization,and reductive elimination steps giving the alkyne addition product.In addition,the influence of substituent in SPO on reaction mechanism and the regio-selectivity of phenylpropyne in reaction have been calculated in detail.