Theoretical elucidation on the regio-, diastereo-, and enantio-selectivities of chiral primary-tertiary diamine catalyst for asymmetric direct aldol reactions of aliphatic ketones.
The asymmetric direct aldol reactions of aliphatic ketones (acetone, butanone, and cyclohexanone) with 4-nitrobenzaldehyde catalyzed by a chiral primary-tertiary diamine catalyst (trans-N,N-dimethyl diaminocyclohexane) have been investigated by performing density functional theory calculations to rationalize the experimentally observed stereoselectivities. Focused on the crucial C-C bond-forming steps, we located several low-lying transition states and predicted their relative stabilities. The calculated results demonstrate that the catalytic direct aldol reactions of acetone favors the (S)-enantiomer and that butanone prefers the branched syn-selective product, while cyclohexanone yields predominantly the opposite anti-selective product. The theoretical results are in good agreement with the experimental findings and provide a reasonable explanation for the high enantioselectivity and diastereoselectivity, as well as regioselectivity, of the aldol reactions under consideration.
Key Lab of Colloid and Interface Chemistry, Ministry of Education, Institute of Theoretical Chemistry, Shandong University, Jinan, 250100, People's Republic of China.
Xiangting
X
Sun
Rongxiu
R
Zhu
Jun
J
Gao
Dongju
D
Zhang
Dacheng
D
Feng