Journal
ACS CATALYSIS
Volume 5, Issue 6, Pages 3731-3739Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acscatal.5b00438
Keywords
asymmetric reaction; Lewis acid catalyst; aqueous media; Global Reaction Root Mapping; density functional theory
Categories
Funding
- MEXT for Innovative Areas (Soft Molecular Systems) [26104519]
- Kyoto University [24245005, 26105733, 15H02158]
- Fukui Fellowship of Kyoto University
- Collaborative Research Program for Young Scientists of ACCMS and IIMC, Kyoto University
- [26810005]
- Grants-in-Aid for Scientific Research [26104519, 26810005, 15KT0142, 26105733] Funding Source: KAKEN
Ask authors/readers for more resources
The aqueous Mukaiyama-Aldol reaction catalyzed by lanthanide (Ln) Lewis add is one of the most attractive reactions for green chemistry. One of the chiral catalysts that achieved a high stereoselectivity is Ln(3+) cornplexed with fluctional DODP, (2R,2'R)-dialkyl 2,2'-(1,7-dioxa-4,10-diazacyclododecane-4,10-diyl)dipropanoates. In this study, we theoretically studied the structure of the Ln3+ DODP (Ln = Eu) complex and the transition states (TSs) for stereodetermining C-C bond formation step between benzaldehyde and silyl enol ether catalyzed by this complex to elucidate the origin of stereoselectivity of the reaction. To explore the local minima and TSs exhaustively, we used an automated exploration method, called the Global Reaction Root Mapping (GRRM) strategy. Unlike conventional rigid chiral catalysts, three conformers of the Eu3+ DODP (the lowest A, the second lowest B, and the third lowest C) coexisted in the reaction system. Considering all the TSs obtained from the three conformers, we reproduced the experimental enantio excess and diastereomeric ratio quantitatively. The most stable TS for the C C bond formation producing the major stereoisomer (R,R) was obtained from the second lowest conformer B. The lowest TS producing the enantiomer (S,S) was obtained from the conformer C; the similar (S,S) TS obtained from the conformer B was 0.4 kcal/mol less stable. Thus, to improve the enantioselectivity, the existing probability of the conformer C had to be reduced. The easiest way to achieve this is replacing Eu3+ by other Ln(3+) with larger ionic radii, which was consistent with the experimental facts.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available