Asymmetric Conjugate Addition Of Diethylzinc Research Articles

Synthesis of novel tartaric acid-derived chiral phosphite ligands and their application in the Cu-catalyzed conjugate addition of diethylzinc to cyclic enones

Five novel tropos (3R,4R)- and/or (3S,4S)-N-benzyltartarimide-derived biphenylphosphite ligands were synthesized and applied in the Cu-catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones with up to 75% e.e. Compared with the reported ligand 1-N-benzylpyrrolidine-3,4-bis[(R)-1,1’-binaphthyl-2,2’-diyl]phosphite-L-tartaric acid, the issue that L-(+)-tartaric acid backbone and (R)-binaphthyl showed strong matched/mismatched character was solved with these tropos ligands. It was found that the enantioselectivity was mainly controlled by the absolute configuration of N-benzyltartarimide backbone, and both enantiomers of the addition products can be obtained by simply changing the configuration of N-benzyltartarimide substituent.

ChemInform Abstract: [2.2]Paracyclophane‐Derived Monodentate Phosphoramidite Ligands for Copper‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Substituted Chalcones.

AbstractCopper‐catalyzed asymmetric conjugate addition of diethylzinc to chalcones is realized by using a newly synthesized [2.2]paracyclophane‐derived monodentate phosphoramidite ligand.

2.2]Paracyclophane-derived monodentate phosphoramidite ligands for copper-catalyzed asymmetric conjugate addition of diethylzinc to substituted chalcones.

Copper-catalyzed asymmetric conjugate addition of diethylzinc to chalcones could be realized by using [2.2]paracyclophane-derived monodentate phosphoramidite ligands. The excellent yield and enantioselectivity (up to 98% yield and 95% enantiomeric excess) could be realized with low catalyst loading of 1.0 mol % and low ligand loading of 1.2%.

Asymmetric Conjugate Addition to Cyclic Enone Catalyzed by Cu‐NHC Complexes with C2 Symmetry

AbstractA series of chiral, C2 symmetric tridentate N‐heterocyclic carbene precursors, containing two N‐functionalized hydroxyl or alkoxyl groups, were synthesized. They were applied to catalyze the asymmetric conjugate addition of diethylzinc to cyclohex‐2‐enone and cyclopent‐2‐enone. Enantioselectivity of corresponding reactions can be accomplished with up to 76% ee, and 65% ee, respectively. Flip of major enantiomer was observed when different bases or copper sources were utilized.

Synthesis of Chiral Bulky Monophosphite Ligands and Their Application in Cu-Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Cyclic Enones

A series of new bulky monophosphite ligands were synthesized from axially chiral BINOL and highly sterically hindered adamantanecarbonyl chloride. These ligands were applied to the Cu-catalyzed asymmetric 1,4-conjugate addition of diethylzinc to cyclic enones and were found to have moderate enantioselectivities (up to 61% ee). The stereochemically matched combination of (S)-BINOL in ligand (S)-(2-(adamantane-1-carboxylic acid)-1,1′-binapthalen-2′-yl)-((S)-1,1′-binaphthalen-2,2′-yl)phosphite induces a moderate enantioselectivity. The sense of enantioselectivity is mainly controlled by the configuration of the 2,2′-o, o-(1,1′-binaphthyl)-dioxo-phosphite moiety of the ligands.

Co-Metal-Free Enantioselective Conjugate Addition Reactions of Zinc Reagents

Asymmetric conjugate addition of diethylzinc to cinnamaldehyde in a co-metal-free fashion by using N,O-ligands with planar and central chirality is described. Different modulations of the ligand structure, including several combinations of the chiral units, indicate that a [2.2]paracyclophane backbone is essential for the activity and the enantioselectivity of the generated active catalyst. By using the optimized ligand, an isolated yield of 90 % was obtained with up to 99 % ee.

Modular Asymmetric Synthesis of P-Chirogenic β-Amino Phosphine Boranes

A short concise route to beta-aminophosphine boranes is presented via the desymmetrization of prochiral phosphine boranes, forming P-chirogenic aldehydes that are rapidly transformed to the target compounds employing reductive amination under microwave irradiation. This sequence provides a modular route to P-chirogenic P,N ligands, and in addition, the intermediate aldehydes are versatile P-chiral building blocks for ligand design in general. An alternative pathway via the corresponding alpha-carboxyphosphines is also described. The ligands were subsequently evalutated in the asymmetric conjugate addition of diethylzinc to trans-beta-nitrostyrene.

A facile synthesis and the asymmetric catalytic activity of BINOL-based thiazole (thiadiazole) thioether ligands

Four new BINOL-based thiazole (thiadiazole) thioether ligands ( S)- 1, ( S)- 2, ( S,S)- 3 and ( S)- 4 were prepared. When their catalytic effectiveness was tested, good results (up to 93% ee and 97% yield) were obtained in the asymmetric addition of diethylzinc to aldehydes while poor results were obtained in the asymmetric conjugate addition of diethylzinc to enones.

Copper‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to α,β‐Unsaturated Imines Derived from α‐Aminoacids. Enantioselective Synthesis of γ‐Substituted α‐Dehydroaminoesters.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Copper-Catalyzed Asymmetric Conjugate Addition of Diethylzinc to α,β-Unsaturated Imines Derived from α-Aminoacids. Enantioselective Synthesis of γ-Substituted α-Dehydroaminoesters

[Structure: see text] A highly enantioselective synthesis of alpha-dehydroaminoacids with a stereogenic center in the gamma position through copper-catalyzed asymmetric conjugate addition of diethylzinc to alpha,beta-unsaturated imines using a TADDOL-derived phosphoramidite complex is reported.

P‐Chiral o‐Phosphinophenol as a P/O Hybrid Ligand: Preparation and Use in Cu‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Acyclic Enones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

P-Chiral o-Phosphinophenol as a P/O Hybrid Ligand: Preparation and Use in Cu-Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Acyclic Enones

[reaction: see text] (S)-2-(tert-Butylmethylphosphino)phenol and its methyl ether were synthesized from tert-butyldichlorophosphine via optically active phosphine-boranes as the intermediates. The former compound was used as a P/O hybrid ligand in the Cu-catalyzed asymmetric conjugate addition of diethylzinc to acyclic enones to achieve high enantioselectivity of up to 96%.

Enantioselective Conjugate Addition of Diethylzinc to Acyclic Enones Using a Copper Phosphino‐Phenol Complex as Catalyst.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantioselective conjugate addition of diethylzinc to acyclic enones using a copper phosphino-phenol complex as catalyst

Newly designed phosphino-phenol 1c was found to be an efficient chiral auxiliary for copper-mediated asymmetric conjugate addition of diethylzinc to acyclic enones. High enantioselectivity up to >99% ee was achieved in the reaction of acyclic α,β-enones.

Diastereoselective Synthesis of Thieno[3′,2′:4,5]cyclopenta[1,2‐d][1,3]oxazolines — New Ligands for the Copper‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Enones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly Enantioselective Copper‐Catalyzed Conjugate Addition of Diethylzinc to Nitroalkenes.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Diastereoselective Synthesis of Thieno[3′,2′:4,5]cyclopenta[1,2‐d][1,3]oxazolines − New Ligands for the Copper‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Enones

AbstractSeveral new ligands featuring a rigid three ring skeleton have been prepared for the first time following a modular approach. Chirality has been introduced by use of an oxazoline moiety fused with a cyclopenta[b]thiophene backbone. The efficiency and stereochemical impact of these ligands on the copper‐catalyzed enantioselective addition of Et2Zn to chalcone was examined and enantiomeric excesses up to 79% were achieved using the ligand (R,R)‐16 substituted with a methyl group at the cyclopenta moiety. Computational and ESI‐mass spectral studies show that these new compounds behave as monodentate ligands towards Cu+. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Highly enantioselective copper-catalyzed conjugate addition of diethylzinc to nitroalkenes.

Copper-catalyzed asymmetric conjugate addition of diethylzinc to nitroalkenes using new chiral monodentate phosphoramidite ligands proceeds with high enantioselectivity up to 99% ee. [reaction: see text]

Synthesis of New Chiral Aryl Diphosphite Ligands Derived from Pyranoside Backbone of Monosacharides and Their Application in Copper‐Catalyzed Asymmetric Conjugate Addition of Diethylzinc to Cyclic Enones

AbstractNew chiral aryl diphosphite ligands based on the pyranoside backbones of glucose and galactose were prepared. These ligands were tested in the Cu‐catalyzed asymmetric conjugate addition of diethylzinc to cyclic enones with up to 88% ee. The stereoselectivity was found to be dependent on the ring size of the substrate as well as the ligand and copper source. The enantioselectivity depends on the absolute configuration of the C‐4 stereogenic center of the ligand backbone, while the sense of enantioselectivity is mainly controlled by the configuration of the binaphthyl phosphite moieties.

New chiral amino-phosphoramidite and bisphosphoramidite ligands derived from ( R, R)-1,2-diaminocyclohexane: application in Cu-catalyzed asymmetric conjugate addition of diethylzinc to 2-cyclohexenone

New bidentate amino-phosphoroamidite and diphosphoroamidite ligands derived from inexpensive ( R, R)-1,2-diaminocyclohexane have been synthesized and screened in the Cu-catalyzed asymmetric conjugate addition of Et 2Zn to 2-cyclohexenone. The highest 74% ee value was reached with the N, N′-dimethyl substituted P, N-ligand and Cu(OAc) 2·H 2O.