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Relevant academic research and scientific papers

Highly Enantioselective Iridium-Catalyzed Hydrogenation of Conjugated Trisubstituted Enones

Asymmetric hydrogenation of conjugated enones is one of the most efficient and straightforward methods to prepare optically active ketones. In this study, chiral bidentate Ir-N,P complexes were utilized to access these scaffolds for ketones bearing the stereogenic center at both the α- and β-positions. Excellent enantiomeric excesses, of up to 99%, were obtained, accompanied with good to high isolated yields. Challenging dialkyl substituted substrates, which are difficult to hydrogenate with satisfactory chiral induction, were hydrogenated in a highly enantioselective fashion.

HIGHLY ENANTIOSELECTIVE ACCESS TO CYCLIC BETA-AMINO ACIDS

Disclosed herein is a method of forming a compound of formula I: wherein the substituents are defined in the specification. In particular, the compounds of formula I can be converted to amino acids bearing quaternary stereocenters with exceptional optical purities.

An entry to non-racemic β-tertiary-β-amino alcohols, building blocks for the synthesis of aziridine, piperazine, and morpholine scaffolds

A method for the preparation of enantiopure β-tert-amino alcohols bearing a tetrasubstituted C-stereocenter, as well as their conversion into selected medicinally privileged heterocyclic systems (morpholines, aziridines, piperazines) is reported. These co

Access to Cyclic β-Amino Acids by Amine-Catalyzed Enantioselective Addition of the γ-Carbon Atoms of α,β-Unsaturated Imines to Enals

Disclosed herein is a new catalytic approach for an efficient access to cyclic β-amino acids widely found in bioactive small molecules and peptidic foldamers. Our method involves addition of the remote γ-carbon atoms of α,β-unsaturated imines to enals by iminium organic catalysis. This highly chemo- and stereo-selective reaction affords cyclic β-amino aldehydes that can be converted to amino acids bearing quaternary stereocenters with exceptional optical purities. Our study demonstrates the unique power of organic catalytic remote carbon reactions in rapid synthesis of functional molecules.

Synthetic Method to Form 2,2′-Bis(naphthoquinone) Compounds

We have discovered a transition-metal-free approach to the synthesis of 2,2′-bis(naphthoquinones) using a Diels-Alder reaction of conjugated ketene silyl acetals with benzoquinone. Its monomer analogue can also be synthesized by simply increasing the equivalents of benzoquinone.

Iridium-catalyzed asymmetric hydrogenation of 3,3-disubstituted allylic alcohols in ethereal solvents

Ir-phosphinomethyl-oxazoline complexes have been identified as efficient, highly enantioselective catalysts for the asymmetric hydrogenation of 3,3-disubstituted allylic alcohols and related homoallylic alcohols. In contrast to other N,P ligand complexes, which require weakly coordinating solvents, such as dichloromethane, these catalysts perform well in more ecofriendly THF or 2-MeTHF. Their synthetic potential was demonstrated with the formal total synthesis of four bisabolane sesquiterpenes. Particularly high enantioselectivity values in the asymmetric hydrogenation of 3,3-disubstituted allylic alcohols and related homoallylic alcohols have been achieved with Ir-phosphinomethyloxazoline catalysts. In contrast to other N,P-ligand complexes, which require weakly coordinating solvents, such as CH 2Cl2, these catalysts perform well in more ecofriendly THF or 2-MeTHF (see scheme; CODa =a 1,5-cyclooctadiene). Copyright

Catalytic asymmetric formation of δ-Lactones from Unsaturated acyl halides

Previously unexplored enantiopure zwitterionic ammonium dienolates have been utilized in this work as reactive intermediates that act as diene components in hetero-Diels-Alder reactions (HDAs) with aldehydes to produce optically active δ-lactones, subunits of numerous bioactive products. The dienolates were generated in situ from E/Z mixtures of a,b- unsaturated acid chlorides by use of a nucleophilic quinidine derivative and Sn (OTf)2 as co-catalyst. The latter component was not directly involved in the cycloaddition step with aldehydes and simply facilitated the formation of the reactive dienolate species. The scope of the cycloaddition was considerably improved by use of a complex formed from Er- (OTf)3 and a simple commercially available norephedrine-derived ligand that tolerated a broad range of aromatic and heteroaromatic aldehydes for a cooperative bifunctional Lewis-acid-/ Lewis-base-catalyzed reaction, providing a,b-unsaturated d-lactones with excellent enantioselectivities. Mechanistic studies confirmed the formation of the dienolate intermediates for both catalytic systems. The active ErIII complex is most likely a monomeric species. Interestingly, all lanthanides can catalyze the title reaction, but the efficiency in terms of yield and enantioselectivity depends directly on the radius of the Ln III ion. Similarly, use of the pseudolanthanides ScIII and YIII also resulted in product formation, whereas the larger La III and other transition metal salts, as well as main group metal salts, proved to be inefficient. In addition, various synthetic transformations of 6- CCl3- or 4-silyl-substituted α,β-unsaturated d-lactones, giving access to a number of valuable δ-lactone building blocks, were investigated.

A flexible route toward polypropylene model compounds of various tacticities

This paper reports the flexible synthesis of 2,4,6,8,10-pentamethylundecane (PMU) as well as a chromatographic method for the separation of its diastereoisomers. This strategy offers a unique opportunity to accede to three model compounds of polypropylene (PP) of different tacticities (i.e., isotactic, syndiotactic, and atactic PP). Georg Thieme Verlag Stuttgart.

Esterase-mediated synthesis of optically active GABA analogues containing a stereogenic all-carbon quaternary carbon atom

Esterase from Horse Liver (HLAP) was able to hydrolyze a series of linear and cyclic β,β-dialkyl-γ-nitroesters, in spite of the well-known reluctance of hydrolytic enzymes to recognize and transform hindered substrates, such as those possessing a stereoge

HOMOALLYL ALCOHOLS USEFUL AS FRAGRANCES

Branched, highly-substituted C9-C13 homoallyl alcohols of formula (I) in which R1 and R2 are selected from H or Me and R3 is selected from H, Me and Et. The compounds are useful in fragrance applications in which a floral note is desired.