Computational Studies On The Divergent Reactions Between α-imino Rhodium Carbenoids And 1,3-diketones And The Mechanisms Of Gold-Catalyzed Alkyne Cyclization

The reaction between metal carbene and nucleophile is one of the most important methods for the efficient synthesis of C-X bond heterocyclic compounds.Traditionally,diazo compounds are commonly used for the generation of the corresponding carbenes.However,the instability of many diazo compounds limits their applications in syntheses.Therefore,identifying sustainable and stable surrogates for carbene precursor has attracted great attention.N-sulfonyl-1,2,3-triazole,as carbene precursors,is converted into a-Imino rhodium carbenoids.The characteristic imine functionality adjacent to the carbenoid center renders the carbene species especially suitable for the synthesis of various heterocycles.In this paper,the density functional theory(DFT)were carried out to investigate the divergent reactions between α-Imino Rhodium Carbenoids and 1,3-Diketones cyclization reaction.The divergent reaction was determined to be dependent on the type of 1,3-diketones,as acyclic 1,3-ketones resulted in 2-acetylpyrroles,whereas cyclic 1,3-diketones chemoselectively afforded α-amino ketone or 2,3-fused pyrroles.The reactions could be explained by the formation of the distinct intermediates with different geometries.The factors accounting for the chemo-and regio-selectivities may attribute to the formation of the hydrogen bond,steric hindrance,electron effects.For the perspective of the theoretical calculation theory,deepening the understanding of the selectivity of this type of nucleophilic addition reactions.Recently,the addition reaction of univalent gold-catalyzed alkynes has been widely used in the field of organic synthesis,and whether the a-oxo gold carbene as a key intermediate still a hot pot.We have studied the mechanisms of Au(I)-catalysed intramolecular addition of the hydroxylamine group onto alkynes to explore the origin of the reactions.The terminal alkyne to afford 3-pyrrolidinone(favors the 5-exo O-attack cyclization),while the nitrone product is synthesized for the phenyl-substituted alkyne(favors 5-endo N-attack cyclization).It is worthnoting that the counterion effect may account for the origin of chemo-and regio-selectivities reaction.And the a-oxo gold carbenoid intermediate have a higher energy barrier in this reaction.The factors accounting for the chemo-and regio-selectivities of the reaction:(1)the nucleophilic ability of the nitrogen and oxygen atoms of the substrate.(2)the electrophilicity of the terminal alkyne and the internal alkyne.(3)stability of cyclization intermediates.