How far is far? Weak noncovalent interactions govern enantioselective cyclopropanation catalyzed by ruthenium phthalocyanine with remote (R)-BINOL substituents
Alexander A. Dmitrienko , Andrey P. Kroitor , Liudmila I. Demina , Gayane A. Kirakosyan , Yulia G. Gorbunova , Aslan Yu. Tsivadze , Alexander G. Martynov , Alexander B. Sorokin
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引用次数: 0
Abstract
A chiral bis-(R-binaphthoxy)-bridged ruthenium phthalocyanine complex was synthesized and examined in the cyclopropanation of styrene derivatives with diazo esters. Despite the asymmetry-inducing chiral substituents in the phthalocyanine ligand being positioned at a considerable distance from the catalytic center, the complex exhibits significant stereoselectivity, depending on the nature of the substrates. Specifically, switching from ethyl diazoacetate (EDA) to the bulkier tert-butyl diazoacetate (tBuDA) dramatically improved the trans/cis ratio from 6:1 to 49:1 and the enantiomeric excess from 27 % to 71 % for the (S,S)-cyclopropane derivative of styrene. Furthermore, extremely high trans/cis ratios (up to 499:1) and promising enantiomeric excesses (up to 83 %) were achieved using various substituted styrenes. Most reactions were carried out with an exceptionally low catalyst loading of 0.02 mol%. A detailed DFT computational study of the reaction between styrene and tBuDA accurately reproduced the experimental cyclopropanation enantioselectivity, explaining the preferential formation of the (S,S)-cyclopropane derivative. Non-covalent interaction analysis within quantum theory of atoms in molecules (QTAIM) and energy decomposition analysis (ETS-NOCV) both revealed that weak interactions played a crucial role in stabilizing the enantio-determining transition states. This work firmly demonstrates that a catalytic system with a properly designed rigid chiral cavity combined with an appropriate carbene can achieve promising asymmetric induction, even when the chiral substituents are remote from the catalytic center.
期刊介绍:
The Journal of Catalysis publishes scholarly articles on both heterogeneous and homogeneous catalysis, covering a wide range of chemical transformations. These include various types of catalysis, such as those mediated by photons, plasmons, and electrons. The focus of the studies is to understand the relationship between catalytic function and the underlying chemical properties of surfaces and metal complexes.
The articles in the journal offer innovative concepts and explore the synthesis and kinetics of inorganic solids and homogeneous complexes. Furthermore, they discuss spectroscopic techniques for characterizing catalysts, investigate the interaction of probes and reacting species with catalysts, and employ theoretical methods.
The research presented in the journal should have direct relevance to the field of catalytic processes, addressing either fundamental aspects or applications of catalysis.