.pi.-Stacking and the platinum-catalyzed asymmetric hydroformylation reaction: a molecular modeling study

Castonguay, Laurie A.; Rappé, Anthony K.; Casewit, C. J.

doi:10.1021/ja00019a013

Cited by 66 publications

(28 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At lower temperatures, the secondary a-methylbenzyl intermediate 8 is more stable than the phenethyl intermediate 9 by 4 -6 kJ/mol, as has been shown for similar systems by Rappé and co-workers (Fig. 4) [42]. The a-methylbenzyl intermediate 8 will, therefore, be the preferred intermediate at lower temperature.…”

Section: Results Andsupporting

confidence: 69%

Chiral (Diphosphonite)platinum Complexes in Asymmetric Hydroformylation

Duren

Cornelissen

Vlugt

et al. 2006

Helvetica Chimica Acta

View full text Add to dashboard Cite

Dedicated to Professor Giambattista Consiglio on the occasion of his 65th birthdayThe chiral diphosphonite ligand (11bR,11'bR)-4,4'-(9,9-dimethyl-9H-xanthene-4,5-diyl)bis[dinaphtho[2,1-d:1',2'-f][1,3,2]dioxaphosphepin] ((R,R)-XantBino; (R)-1), based on a rigid xanthene backbone, was applied in the Pt/Sn-catalyzed hydroformylation of styrene (4a), 4-methylstyrene (4b), vinyl acetate (4c), and allyl acetate (4d), by using a Pt/Sn ratio of 1 : 1. High ee of up to 80% were observed, along with good regioselectivities towards the desired branched aldehydes. For styrene, an interesting inversion in the stereoselection process was observed at elevated temperatures, and a mechanism is proposed considering the temperature dependence of the regioselectivity. Introduction. -The asymmetric hydroformylation of alkenes is a reaction of great potential for the production of optically active aldehydes, which are versatile building blocks in synthetic organic chemistry [1] [2]. Initial work on asymmetric hydroformylation in the presence of cobalt [3], platinum [4], and rhodium catalysts [5] resulted in very low enantioselectivities, but the Pt/Sn-catalyst, modified with chiral diphosphine ligands and pioneered by Consiglio and co-workers led to much better results than any previous system [6]. However, these catalysts showed poor regioselectivities, yielding the branched, chiral aldehydes in only 50 -70% and in some cases of up to 80% [7]. Additionally, the formation of hydrogenated products and double-bond isomerization as unwanted side reactions were observed.Typically, a large excess of up to 6 equiv. of SnCl 2 was necessary to form stable catalysts and to avoid decomposition to Pt-black. However, this excess causes significant product racemization, as observed problem for the early systems, leading to lower overall enantioselectivities [6]. To overcome these drawbacks, trapping agents, e.g., triethyl orthoformate (HC(OEt) 3 ) were added, to achieve in situ protection of the aldehyde and to reach high enantioselectivities of up to 96% [8] [9]. Alternatively, preformation of the Pt/Sn bimetallic catalyst species resulted in higher enantioselectivities as well as chemo-and regioselectivities [10] [11].

show abstract

Section: Results Andsupporting

confidence: 69%

Chiral (Diphosphonite)platinum Complexes in Asymmetric Hydroformylation

Duren

Cornelissen

Vlugt

et al. 2006

Helvetica Chimica Acta

View full text Add to dashboard Cite

show abstract

“…30c). 301 The combination of hydrophobic interactions and weak attractive interactions allows for the encapsulation and the reaction of substrate(s) within the inner space of well-defined molecular hosts (Part 2). 11,14,16,46 Recently, the aromatic rings of well-designed ligands have been used to create an aromatic p-wall surrounding the metal centre.…”

Section: Ligand-substrate Interactionmentioning

confidence: 99%

Supramolecular catalysis. Part 1: non-covalent interactions as a tool for building and modifying homogeneous catalysts

et al. 2014

View full text Add to dashboard Cite

Supramolecular catalysis is a rapidly expanding discipline which has benefited from the development of both homogeneous catalysis and supramolecular chemistry. The properties of classical metal and organic catalysts can now be carefully tailored by means of several suitable approaches and the choice of reversible interactions such as hydrogen bond, metal-ligand, electrostatic and hydrophobic interactions. The first part of these two subsequent reviews will be dedicated to catalytic systems for which non-covalent interactions between the partners of the reaction have been designed although mimicking enzyme properties has not been intended. Ligand, metal, organocatalyst, substrate, additive, and metal counterion are reaction partners that can be held together by non-covalent interactions. The resulting catalysts possess unique properties compared to analogues lacking the assembling properties. Depending on the nature of the reaction partners involved in the interactions, distinct applications have been accomplished, mainly (i) the building of bidentate ligand libraries (intra ligand-ligand), (ii) the building of di- or oligonuclear complexes (inter ligand-ligand), (iii) the alteration of the coordination spheres of a metal catalyst (ligand-ligand additive), and (iv) the control of the substrate reactivity (catalyst-substrate). More complex systems that involve the cooperative action of three reaction partners have also been disclosed. In this review, special attention will be given to supramolecular catalysts for which the observed catalytic activity and/or selectivity have been imputed to non-covalent interaction between the reaction partners. Additional features of these catalysts are the easy modulation of the catalytic performance by modifying one of their building blocks and the development of new catalytic pathways/reactions not achievable with classical covalent catalysts.

show abstract

“…[35][36][37] The monomer model was constructed with a Builder module in Cerius 2 . The crystalline structure of 7,7Ј-bis[(aza-18-crown-6)carbonyl]thioindigo determined by X-ray analysis was used as a reference.…”

Section: Molecular Modeling and Calculationsmentioning

confidence: 99%