Iron-Catalyzed Asymmetric Carboazidation of Styrenes
H. Bao and X. Zhang report on the Fe-catalyzed asymmetric carboazidation of styrenes including mechanistic studies
Professor Hongli Bao (Fujian Institute of Research on the Structure of Matter, CAS, P. R. of China) recalls that one particular research question puzzled her at the onset of the research program that eventually led to the title paper: what will happen when a carbon radical meets a metal species? Possible scenarios include “1) single electron transfer from the radical to the metal-ligand (M-G) species, forming a carbon cation which is subsequently either deprotonated or attacked by nucleophiles in the reaction environment; 2) ligand (G) transfer from the metal species M-G to the radical without obvious interaction between two reactants; this process is also called outer-sphere group transfer or radical substitution mechanism by other chemists; 3) the radical combines with the M-G metal species forming a high valent metal species M(n+2), which undergoes reductive elimination to deliver a product; the latter reaction mode is known as inner-sphere pathway. According to Professor Bao, among these three modes, normally the inner-sphere pathway is utilized in asymmetric synthesis, given that the C–M bond brings two coupling partners close in a chiral environment. Her research group is extremely interested in seeking to achieve stereocontrol in the outer-sphere radical reactions by harnessing weak interactions.
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