open access

https://hdl.handle.net/2115/90550

Asymmetric Dehydrative Cyclization of Allyl Alcohol to Cyclic Ether Using Chiral Bronsted Acid/CpRu(II) Hybrid Catalysts : A DFT Study of the Origin of Enantioselectivity

英語

2022-10-07

American Chemical Society

Journal of organic chemistry

87(19)

13062-13072

To elucidate the reaction mechanism and the origin of the enantioselectivity of the asymmetric dehydrative cyclization of allyl alcohol to cyclic ether catalyzed by a Cp-ruthenium complex and a chiral pyridinecarboxylic acid, (R)-X-NaphPyCOOH, density functional theory (DFT) calculations were performed. According to the DFT calculations, the rate determining step is the dehydrative sigma-allyl formation step with delta G(& Dagger; ) = 18.1 kcal mol(-1) at 80 ?. This agrees well with the experimental data (delta G(& Dagger;) = 19.01 kcal mol(-1) at 80 ?). The DFT result showed that both hydrogen and halogen bonds play a key role in the high enantioselectivity by facilitating the major R,SRu- catalyzed reaction pathway via a sigma-allyl Ru intermediate to generate the major (S)-product. In contrast, the reaction is sluggish in the presence of the diastereomeric R,RRu catalyst with an apparent activation energy of 33.1 kcal mol(-1); the minor (R)-product is formed via a typical pi-allyl Ru intermediate and via a minor pathway for the cyclization step. In addition, the calculated activation Gibbs free energies, 14.4 kcal mol(-1) for I < 16.8 kcal mol(-1) for Br < 18.1 kcal mol(-1) for Cl, reproduced the observed halogen-dependent reactivity with the (R)-X-Naph-PyCOOH ligands. The origin of the halogen trend was clarified by a structural decomposition analysis.

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Accepted Manuscript

This document is the Accepted Manuscript version of a Published Work that appeared in final form in [Journal of organic chemistry], copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see [https://pubs.acs.org/articlesonrequest/AOR-BG29UG6RSNBAEAQU3UBD].

0022-3263