On-surface stereoconvergent synthesis, dimerization and hybridization of organocopper complexes

Despite the vital role of stereoconvergent synthesis in modern chemistry, the on-surface stereoconvergent synthesis of organometallic complexes involving transformation among several stereoisomers to one specific form has been few reported. By combination of high-resolution scanning tunneling microscopy(STM) imaging/manipulation and density functional theory(DFT) calculations, we have displayed the stereoconvergent synthesis of organocopper complexes via the Cu-alkene interaction and further dimerization into H-shaped motifs, in which two cis-forms and one trans-form are involved, and the specific adsorption configuration of one cis-form is revealed to be the key for such a synthesis. Furthermore, the generality of the dimerization of organocopper complexes has also been verified by codeposition of two similar molecular precursors, and the hybridized K-shaped motifs(made up of two kinds of organocopper complexes) have been successfully achieved. These findings may provide atomic-scale insights into the synthesis of specific stereoisomers in the fields of pharmaceuticals, biochemistry and organometallic chemistry.

Stereoconvergent and stepwise 1,3-dipolar cycloadditions of nitrile oxides and nitrile imines

The first example of stereoconvergent 1,3-dipolar cycloaddition of nitrile oxides and nitrile imines with E/Z isomeric mixture of electron-deficient olefins is reported,delivering isoxazolines and pyrazolines bearing two vicinal stereogenic tertiary and trifluoromethylated quaternary carbon centers with perfect regioand diastereoselectivities.The possibility of concerted cycloaddition/epimerization sequence under basic condition to form the thermodynamically stable diastereomers is excluded through some control experiments and DFT calculations,and a stepwise mechanism is proposed.