Dalian Institute of Chemical Physics (DICP) research group led by Prof. HU Xiangping made a new progress in the copper-catalyzed asymmetric propargylic transformation. By employing a desilylation-activated strategy, they successfully realized a copper-catalyzed asymmetric [3+2] cycloaddition of propargylic esters with β-naphthol or electron-rich phenol derivatives. This work has now been published in Angew. Chem. Int. Ed. 2016, 55, 5014-5018.
A new process of a copper-catalyzed asymmetric [3+2] cycloaddition of propargylic esters with β-naphthol or electron-rich phenol derivatives (Image by SHAO Long)
The key to realize the propargylic transformations is how to effectively form the active intermediates, copper allenylidene complexes. Due to the insufficient ability of terminal propargylic esters towards the copper allenylidene complexes in the traditional methods, a new strategy or method is therefore highly anticipated. Considering copper could efficiently promoted Csp-Si bond cleavage in Sonogashira cross-coupling reaction, researchers believe that the similar desilylation-activated strategy could also provide a powerful solution to the formation of copper allenylidene active intermediates. It can be generated irreversibly by the desilylation of 3-trimethylsilylpropargylic substrates with chiral copper complexes.
Based on this strategy, researchers successfully realized the asymmetric [3+2] cycloaddition of propargylic esters with β-naphthol or electron-rich phenol derivatives by the use of a sterically hindered chiral tridentate ketimine P,N,N-ligand developed in the same group. This represents an alternative asymmetric activation strategy in propargylic transformations, following the decarboxylative propargylic transformation strategy proposed by the same research group in 2014(Angew. Chem. Int. Ed. 2014, 53, 1410-1414). These synthetic strategies significantly advance the research in the catalytic asymmetric propargylic transformation.
This work is financially supported by DICP and National Natural Science Foundation of China. (Text and Image by SHAO Long)
Dr. LU Xinyi
Dalian Institute of Chemical Physics, Chinese Academy of Sciences,
457 Zhongshan Road, Dalian, 116023, China,