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DFT Studies on Copper-Catalyzed Dearomatization of Pyridine
journal contribution
posted on 2020-08-12, 11:45 authored by Linlin Wu, Fu Kit Sheong, Zhenyang LinA systematic theoretical study has
been performed with the aid
of density functional theory (DFT) calculations on the mechanism of
asymmetric 1,4-dearomatization of free pyridine with styrene and dimethoxy(methyl)silane
(HSiMe(OMe)2) catalyzed by copper complexes. Two proposed
mechanisms, dearomatization of pyridine catalyzed by cooperation of
two copper(I) centers and by one copper(I), are calculated and analyzed.
The results indicate that one copper(I) center is capable of catalyzing
the dearomatization reaction. To achieve the dearomatization on one
copper(I) center, the Cu–H addition “product”
(derived from styrene insertion into Cu–H) undergoes 1,3- and
1,5-Cu migration on a benzylic ligand, facilitating the 1,2- and 1,4-dearomatization
of pyridine. In the two metal-center mechanism, significant sterically
repulsive interactions among the substituents on the ligands between
the two metal fragments hindered the dearomatization process. The
origin of selectivity between 1,2- and 1,4-dearomatization of pyridine
has also been discussed.
