Density functional computations of alkynylation of ethanimine catalyzed by chiral zinc(II)‐complexes

Abstract

ABSTRACT:The alkynylation of ethanimine catalyzed by chiral zinc(II)-complexes was studied by means of the density functional theory (DFT). All the intermediates and transition states were optimized completely at the B3LYP/6-31G(d,p) level. Calculation results confirm that the alkynylation of ethanimine is exothermic and the total released energy is about Ϫ13 kJ/mol. The formation of the catalyst-alkynyl complexes M4 is the rate-determining step for this alkynylation, and the formation of the catalyst-amine complexes M5 is the chirality-limiting step for this alkynylation. The transition states for the chirality-limiting step have a HOOOZnOCOCON six-membered ring. The dominant products predicted theoretically for this alkynylation are, respectively, Samine for ethanimine anti and R-amine for ethanimine syn.

Density functional computations of alkynylation of nitrones catalyzed by chiral zinc(II)-complexes

“…Carreira's group has examined many researches on the enantioselective addition of terminal alkynes to aldehydes or imines and suggested a single-zinc model of reaction mechanism [2,[8][9][10][11][12][13][14][15]. The reaction mechanism of zinccatalyzed alkynylation of aldehydes or ethanimine has been investigated by our group at B3LYP/6-31G(d,p) level [26,27]. However, theoretical data available for the mechanism of the addition of terminal alkynes to nitrones are rather limited, and these quantum chemical studies on the mechanism of single-zinc-catalyzed alkynylation of nitrones are hardly reported.…”