Asymmetric Ullmann Coupling Research Articles

Synthesis of Axially Chiral 2,2'-Bisphosphobiarenes via a Nickel-Catalyzed Asymmetric Ullmann Coupling: General Access to Privileged Chiral Ligands without Optical Resolution.

We report an asymmetric homocoupling of ortho-(iodo)arylphosphine oxides and ortho-(iodo)arylphosphonates resulting in highly enantioenriched axially chiral bisphosphine oxides and bisphosphonates. These products are readily converted to enantioenriched biaryl bisphosphines without need for chiral auxiliaries or optical resolution. This provides a practical route for the development of previously uninvestigated atroposelective biaryl bisphosphine ligands. The conditions have also proven effective for asymmetric dimerization of other, non-phosphorus-containing aryl halides.

Development and Challenges in Copper-Catalyzed Asymmetric Ullmann-Type Coupling Reactions

Ullmann-type coupling is one of the most powerful methods for the formation of aryl C–C, C–N, and C–O bonds. Yet asymmetric Ullmann coupling has received little attention because of the great challenges in both ligand and reaction designs. The success of the first catalytic enantioselective intramolecular Ullmann C–N coupling reaction through an asymmetric desymmetrization strategy offers a new way to develop enantioselective variants of such reactions. This paper addresses the importance of the desymmetrization strategy in Ullmann-type couplings and outlines some future directions in this field.

ChemInform Abstract: Nickel‐Catalyzed Asymmetric Ullmann Coupling for the Synthesis of Axially Chiral Tetra‐ortho‐Substituted Biaryl Dials.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Asymmetric Ullmann Coupling of Biaryl Dials Catalyzed by Nickel

Axially chiral biaryl moieties are common in natural products. The authors developed the first nickel-catalyzed asymmetric Ullmann coupling for substituted aryl halides to yield axially chiral biaryls, and applied this method to the formal synthesis of the natural product (+)-isoschizandrin.

Nickel-Catalyzed Asymmetric Ullmann Coupling for the Synthesis of Axially Chiral Tetra-ortho-Substituted Biaryl Dials

The first example of nickel-catalyzed asymmetric Ullmann coupling of bis-ortho-substituted arylhalides is described. With the chiral BINOL-based monodentate phosphoramidite ligand, the reaction allows atropoenantioselective synthesis of a series of axially chiral tetra-ortho-substituted biaryl dials. By taking advantage on this asymmetric Ullman coupling as a key stereogenic axis-forming reaction, the formal synthesis of (+)-isoschizandrin was accomplished.

Total Syntheses of (−)-Herbertenediol, (−)-Mastigophorene A, and (−)-Mastigophorene B. Combined Utility of Chiral Bicyclic Lactams and Chiral Aryl Oxazolines

A nonracemic bicyclic lactam has been used to construct a chiral cyclopentane containing vicinal quaternary carbon centers in optically pure form, which is common to all of the title compounds. An oxazoline-mediated asymmetric Ullmann coupling was then utilized to establish chirality about the biaryl axis of mastigophorenes A and B. Through the course of this synthesis, it was clearly demonstrated that smaller chiral auxiliaries lead to higher levels of atroposelection, a previously unknown phenomenon of the asymmetric Ullmann coupling.

ChemInform Abstract: The Synthesis of (S)‐(+)‐Gossypol via an Asymmetric Ullmann Coupling.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis and chiroptical properties of a novel C2-symmetric binaphthyl phosphortriamide ("chiral HMPA").

By use of an asymmetric Ullmann coupling involving chiral naphthalene oxazolines 1, the title compounds were prepared in good yields and with high diastereoselectivity. Hydrolysis of the binaphthyl oxazolines 2 led to the di-aldehydes 5, which were transformed into the azepine derivative, 6. The latter was treated with the appropriate phosphoryl halide to access the chiral HMPA systems 7 and 9. The CD spectra of the chiral azepine 6 and the chiral phosphoramides 7 and 9 were measured and showed a strong positive CD couplet near 225 nm, consistent with the P axial chirality (S configuration). Semi-empirical CNDO/S molecular orbital calculations of the CD spectrum of 6 satisfactorily reproduced the major features of the observed spectrum.

The first synthesis of optically pure (+)- and (−)-isokotanin A and the assignment of their absolute configuration

The first asymmetric synthesis of optically pure (+) and (−)-Isokotanin A is described. The key steps involve the asymmetric Ullmann coupling and selective demethylation. The absolute configuration of the naturally occuring (+)-Isokotanin A is assigned as a R.

A Rapid Total Synthesis of an Ellagitannin

The ellagitannins are galloyl esters of glucose that contain at least one chiral biaryl (digalloyl) subunit. Included in this family are the tellimagrandins (1-3). The first asymmetric synthesis of (S)-4,4',5,5',6,6'-hexamethoxy-2,2'-diphenic acid, a ubiquitous subunit in ellagitannins, is reported by utilization of an intermolecular oxazoline-mediated asymmetric Ullmann coupling. Attachment of this acid to an appropriate glucose core resulted in the synthesis of an ellagitannin

The Asymmetric Ullmann Coupling Reaction of (S)-2,2′-Bis(1-bromo-2-naphthoyloxy)-1,1′-binaphthyl Revisited. Formation of 24-Membered Optically Pure Cyclic Dimer as Well as 12-Membered Cyclic Monomer

Abstract The copper-promoted Ullmann reaction of the title diester proceeded with high stereoselectivity to give 24-membered optically pure cyclic dimer of (S,S,S,S)-configuration as well as 12-membered monomeric cycle of (S,S)-configuration. The reaction also gave reduced, open-chain dimer enriched in (S,R,S)-diastereomer over (S,S,S)-counterpart (17% d.e.). Stereochemical course to the cyclic dimer was discussed considering the result that the intermolecular Ullmann coupling of chiral alcohol esters of 1-bromo-2-naphthoic acid poorly induced axial chirality in the joining of the two naphthyl units.