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Relevant academic research and scientific papers

Computationally guided design of a readily assembled phosphite-thioether ligand for a broad range of pd-catalyzed asymmetric allylic substitutions

A modular approach employing indene as common starting material, has enabled the straightforward preparation in three reaction steps of P-thioether ligands for the Pd-catalyzed asymmetric allylic substitution. The analysis of a starting library of P-thioether ligands based on rational design and theoretical calculations has led to the discovery of an optimized anthracenethiol derivative with excellent behavior in the reaction of choice. Improving most approaches reported to date, this ligand presents a broad substrate and nucleophile scope. Excellent enantioselectivities have been achieved for a range of linear and cyclic allylic substrates using a large number of C-, N-, and O-nucleophiles (40 compounds in total). The species responsible for the catalytic activity have been further investigated by NMR in order to clearly establish the origin of the enantioselectivity. The resulting products have been derivatized by means of ring-closing metathesis or Pauson-Khand reactions to further prove the synthetic versatility of the methodology for preparing enantiopure complex structures.

Amino-P Ligands from Iminosugars: New Readily Available and Modular Ligands for Enantioselective Pd-Catalyzed Allylic Substitutions

The construction of a novel class of amino-phosphite/phosphinite/phosphine ligands containing a protected pyrrolidine-3,4-diol moiety is presented. These ligands are obtained from readily available sugars. They thus contain the advantages of carbohydrates in terms of selection of the stereogenic carbons, polyfunctional groups able to modulate the electronic and steric properties, and the general good stability of carbohydrate derivatives. They constitute a novel class of P,N-ligands that have been used in the enantioselective allylic substitutions of acyclic and cyclic substrates with varied electronic and steric requirements, using different C- and N-nucleophiles, with high enantioselectivities. Among the three groups of P,N-ligands (amino-P; P = phosphite, phosphinite, and phosphine groups) the new amino-phosphite ligands give the widest substrate and nucleophile scope, including the more challenging hindered linear and cyclic substrates. In particular, for carbohydrate-derived amino-phosphite ligands and linear substrates, high enantioselectivity in the reactions requires an R configuration of the binaphthyl moiety. However, for cyclic substrates both product enantiomers can be reached by setting out the chirality of the binaphthyl phosphite moiety. A detailed investigation of the appropriate Pd intermediates is also presented.

Chiral oxazoline NNP type ligands as well as synthesis method and application thereof

The invention relates to chiral oxazoline NNP type ligands as well as a synthesis method and an application thereof. The ligands adopt the structure shown in general formula 1 or 2. During preparation, a chiral ligand 1 and a chiral ligand 2 are prepared from Fmoc-Cl and a chiral amino acid compound 3 used as initial raw materials through multi-step reactions. The ligands can be applied to catalytic synthesis of chiral beta ketone ester fluoride and synthesis of propanedione derivatives and chiral malonate derivatives through palladium-catalyzed asymmetric allyl substitution reactions. Compared with the prior art, the reaction condition is mild, operation is easy, repeatability is good, mass preparation can be realized, and the prepared catalyst has higher ee value and yield when applied to beta ketone ester fluoridation and palladium-catalyzed asymmetric allyl substitution reactions.

Theoretical and Experimental Optimization of a New Amino Phosphite Ligand Library for Asymmetric Palladium-Catalyzed Allylic Substitution

A new library of modular amino phosphite ligands obtained in a few synthetic steps from enantiopure amino alcohols has been tested in asymmetric Pd-catalyzed allylic substitution. The modular ligand design is crucial to find highly selective catalysts for each substrate type using a wide range of C-, N-, and O-nucleophiles. A DFT study of the species responsible for the enantiocontrol was used to optimize the ligand structure. By selecting the ligand components, we were able to identify unprecedented catalytic systems that can create new chiral C-C, C-N, and C-O bonds in a variety of substrate types (hindered and unhindered) in high yields and enantioselectivities (ee values up to 99 %). Further studies on the Pd-π-allyl intermediates provided a deep understanding of the effect of ligand structure in the origin of enantioselectivity. Potential applications of the new Pd/amino phosphite catalysts were demonstrated by the practical synthesis of a range of chiral carbocycles by simple tandem reactions, with no loss of enantioselectivity.

A new modular phosphite-pyridine ligand library for asymmetric Pd-catalyzed allylic substitution reactions: A study of the key Pd-π-allyl intermediates

A library of phosphite-pyridine ligands L1-L12 a-g has been successfully applied for the first time in the Pd-catalyzed allylic substitution reactions of several di- and trisubstituted substrates by using a wide range of C, N and O nucleophiles, among which are the little studied α-substituted malonates, β-diketones, and alkyl alcohols. The highly modular nature of this ligand library enables the substituents/configuration at the ligand backbone, and the substituents/configurations at the biaryl phosphite moiety to be easily and systematically varied. We found that the introduction of an enantiopure biaryl phosphite moiety played an essential role in increasing the versatility of the Pd-catalytic systems. Enantioselectivities were therefore high for several hindered and unhindered di- and trisubstituted substrates by using a wide range of C, N and O nucleophiles. Of particular note were the high enantioselectivities (up to>99 % ee) and high activities obtained for the trisubstituted substrates S6 and S7, which compare favorably with the best that have been reported in the literature. We have also extended the use of these new catalytic systems in alternative environmentally friendly solvents such as propylene carbonate and ionic liquids. Studies on the Pd-π-allyl intermediates provide a deeper understanding of the effect of ligand parameters on the origin of enantioselectivity. A library of phosphite-pyridine ligands has been successfully applied in the Pd-catalyzed allylic substitution reactions of several di- and trisubstituted substrates by using a wide range of C, N, and O nucleophiles. By carefully selecting the ligand components, high regio- and enantioselectivities (up to >99 % ee) and good activities have been achieved (see scheme). The NMR studies on the Pd-π-allyl intermediates provide a deeper understanding of the effect of ligand parameters on the origin of enantioselectivity. Copyright

CYCLIC IMIDATE LIGANDS

The present invention relates to a use of a cyclic imidate as a ligand for catalysis in which the ligand contains sub-structure (Y) as a minimal structural motive, wherein the carbon atoms and the nitrogen atom can be optionally substituted by a chemical substituent.

Trans-(2R,3R)-2,3-Diphenylcyclopropane-1,1-dimethanol: A pivotal diol for the synthesis of novel C2-symmetric ligands for asymmetric transition metal catalysis

Various chiral ligands bearing phosphorus or nitrogen donor atoms were obtained in a straightforward manner starting from trans-(2R,3R)- diphenylcyclopropane-1,1-dimethanol as a key structure. These chiral ligands were tested and compared in palladium(0)-

PROCESS FOR PRODUCTION OF OPTICALLY ACTIVE ALLYL COMPOUND

To provide a novel process for producing an optically active allyl compound which is useful as an intermediate raw material for e.g. pharmaceutical products. A process for producing an optically active allyl compound of the formula (4): (wherein “*” repre

Mass spectrometric screening of chiral catalysts by monitoring the back reaction of quasienantiomeric products: Palladium-catalyzed allylic substitution

(Chemical Equation Presented) Back to basics: The principle of microscopic reversibility is the basis of a new screening method for chiral catalysts. Monitoring the back reaction of quasi-enantiomeric allylation products by ESIMS reveals the intrinsic enantioselectivity of palladium catalysts in allylic substitution reactions (see scheme).

Facile one-pot synthesis of cinchona alkaloid-based P,N ligands and their application to Pd-catalyzed asymmetric allylic alkylation

A novel class of bidentate chiral P,N donor ligands based on cinchona alkaloids is described. These ligands are easily synthesized in one-pot from commercially available enantiopure 1,2-diphenyl-1,2-ethanediol and cinchona alkaloids in two steps. Their ap