Chiral Phosphine-Phosphite Ligands Research Articles

Chiral Phosphine-Phosphite Ligands in Asymmetric Gold Catalysis: Highly Enantioselective Synthesis of Furo[3,4-d]-Tetrahydropyridazine Derivatives through [3+3]-Cycloaddition.

The AuI -catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones with azomethine imines regio- and diastereoselectively affords furo[3,4-d]tetrahydropyridazines in a tandem cyclization/intermolecular [3+3]-cycloaddition process under mild conditions. By employing a chiral gold catalyst (prepared in situ from a Taddol-derived phosphine-phosphite ligand, Me2 SAuCl, and AgOTf) high yields and enantioselectivities (up to 94 % yield, up to 96 % ee) are obtained. The method provides an efficient modular route to substituted heterotricyclic furan derivatives and can be easily scaled up (using catalyst loads of only 0.15 mol %).

Broad Scope Synthesis of Ester Precursors of Nonfunctionalized Chiral Alcohols Based on the Asymmetric Hydrogenation of α,β-Dialkyl-, α,β-Diaryl-, and α-Alkyl-β-aryl-vinyl Esters.

The catalytic asymmetric hydrogenation of trisubstituted enol esters using Rh catalysts bearing chiral phosphine-phosphite ligands (P-OP) has been studied. Substrates covered comprise α,β-dialkyl, α-alkyl-β-aryl, and α,β-diarylvinyl esters, the corresponding hydrogenation products being suitable precursors to prepare synthetically relevant chiral nonfunctionalized alcohols. A comparison of reactivity indicates that it decreases in the order: α,β-dialkyl > α-alkyl-β-aryl > α,β-diaryl. Based on the highly modular structure of P-OP ligands employed, catalyst screening identified highly enantioselective catalysts for α,β-dialkyl (95-99% ee) and nearly all of α-alkyl-β-aryl substrates (92-98% ee), with the exception of α-cyclohexyl-β-phenylvinyl acetate which exhibited a low enantioselectivity (47% ee). Finally, α,β-diarylvinyl substrates showed somewhat lower enantioselectivities (79-92% ee). In addition, some of the catalysts provided a high enantioselectivity in the hydrogenation of E/Z mixtures (ca. Z/E = 75:25) of α,β-dialkylvinyl substrates, while a dramatic decrease on enantioselectivity was observed in the case of α-methyl-β-anisylvinyl acetate (Z/E = 58:42). Complementary deuteration reactions are in accord with a highly enantioselective hydrogenation for both olefin isomers in the case of α,β-dialkylvinyl esters. In contrast, deuteration shows a complex behavior for α-methyl-β-anisylvinyl acetate derived from the participation of the E isomer in the reaction.

Features and Application in Asymmetric Catalysis of Chiral Phosphine-Phosphite Ligands.

Chiral phosphine-phosphites are a class of ligands for asymmetric catalysis characterized by two coordinating functionalities with different electronic properties. These ligands also possess a highly modular structure and, due to versatile synthetic processes, they can be tuned precisely in the catalyst optimization process. Research regarding the application of these ligands in several enantioselective catalytic processes has provided outstanding results in a good number of them. These processes include not only Rh catalyzed reactions, such as olefin hydrogenation and hydroformylation, but also other reactions, such as hydrogenation of olefins and imines by Ru complexes, of imines and N-heterocycles by Ir derivatives, allyl alkylation or conjugate addition by Cu catalysts, or hydrocyanation of olefins by Ni ones. Overall, the use of these ligands has led to the preparation of a wide variety of chiral building blocks with high enantiomeric excess. Therefore, phosphine-phosphites have become in an important class of ligands in asymmetric catalysis.

Highly Stereoselective Synthesis and Hydrogenation of (Z)-1-Alkyl-2-arylvinyl Acetates: a Wide Scope Procedure for the Preparation of Chiral Homobenzylic Esters

A synthesis of (Z)-1-alkyl-2-arylvinyl acetates 3 with broad scope is reported by using two complementary methods. The first one uses a stereospecific gold-catalyzed addition of acetic acid to 1-iodo-alkynes, followed by a Suzuki coupling. By the second, 1-methyl-2-arylvinyl substrates have been obtained selectively as the Z isomers by O-acylation of enolates of methyl benzyl ketones. In addition, the asymmetric hydrogenation of enol esters 3 has been covered for the first time. Using rhodium catalysts based on chiral phosphine-phosphite ligands (P-OP), highly enantioselective hydrogenations (up to 99% ee) have been achieved for a wide range of substrates. Thus, the synthesis and enantioselective hydrogenation of 3 provides a convenient and versatile procedure for the synthesis of valuable chiral homobenzylic esters.

TARTROL-derived chiral phosphine–phosphite ligands and their performance in enantioselective Cu-catalyzed 1,4-addition reactions

By using (R,R,R,R)-2,3-dimethoxy-2,3-dimethyl-1,4-dioxane-5,6-bis-diphenylmethanol (TARTROL) as a chiral building block, a set of six modular phosphine–phosphite ligands (with a 1,2-phenylene backbone) were synthesized and evaluated in the Cu-catalyzed asymmetric 1,4-addition of Grignard reagents to cyclohexenone. Ligands with bulky substituents at the ortho- and para-positions to the chiral phosphite moiety were found to be the most selective affording the 1,4-addition products with enantioselectivities of up to 84% ee.

ChemInform Abstract: Enantioselective Nickel‐Catalyzed Hydrocyanation of Vinylarenes Using Chiral Phosphine—Phosphite Ligands and TMS‐CN as a Source of HCN.

AbstractThe absolute configuration of compound (IIIb) was determined to be (S) by chemical transformation to (S)‐(+)‐ibuprofen.

A Scalable Synthesis of Chiral Modular Phosphine-Phosphite Ligands

The outstanding usefulness of phenol-derived chiral phosphine–phosphite ligands has recently been shown in a number of transition-metal-catalyzed C–C bond-forming reactions. This is exemplified by the synthesis of five new ligands in an optimized procedure that can be reliably performed on a multigram scale.

Enantioselective Nickel‐Catalyzed Hydrocyanation of Vinylarenes Using Chiral Phosphine–Phosphite Ligands and TMS‐CN as a Source of HCN

Enantioselective Nickel‐Catalyzed Hydrocyanation of Vinylarenes Using Chiral Phosphine–Phosphite Ligands and TMS‐CN as a Source of HCN

Synthesis, Characterization, and Reactivity of Ruthenium Bis-Allyl Complexes with Chiral Phosphine-Phosphite Ligands

A series of ruthenium bis-allyl complexes of formula Ru(η3-2-MeC3H4)2(P-OP) (1) which incorporate chiral phosphine-phosphite ligands (P-OP) have been prepared and characterized. Compounds 1 exist in solution as a mixture of two diastereomers (maj and min) differing in the configuration at the metal. Both isomers are in equilibrium in solution, and their ratio varies with the nature of the P-OP ligand. Along the series, higher values of the maj/min ratio were observed with complexes bearing less sterically encumbered phosphite groups. In reactions of compounds 1 with protic reagents removal of one or two allyl ligands has been observed. Thus, reaction of 1h with pentachlorophenol produces the mixed allyl-phenoxide 3h, whereas reaction of 1a or 1h with tiglic acid produces the corresponding tiglates 4a,h, respectively. In addition, compounds 1 generate active catalysts for the hydrogenation of tiglic and 2-methyl-2-pentenoic acids. By appropriate optimization of the structure of the P-OP ligand, enantiosele...

ChemInform Abstract: Chiral Phosphine—Phosphite Ligands in the Enantioselective 1,4‐Addition of Grignard Reagents to α,β‐Unsaturated Carbonyl Compounds.

AbstractCopper‐catalyzed asymmetric 1,4‐addition of Grignard reagents towards cyclic ketones proceeds efficiently in the presence of novel chiral phosphine—phosphite ligands (I) to give the adducts (IV) and (VI) in up to 93% optical purity.

Chiral phosphine–phosphite ligands in the enantioselective 1,4-addition of Grignard reagents to α,β-unsaturated carbonyl compounds

A library of chiral phosphine–phosphite ligands was evaluated in the Cu-catalyzed asymmetric 1,4-addition of Grignard reagents to cyclopentenone, cycloheptenone and 5,6-dihydro-2 H-pyran-2-one. TADDOL-based ligands 1a and 1b with a bulky substituent at the ortho-position to the chiral phosphite moiety gave rise to the 1,4-addition products with high enantioselectivities (up to 93% ee). In addition to ethyl-MgBr (as a standard alkyl nucleophile) phenyl- and isopropenyl-MgBr could also be employed. In the case of cyclopentenone, the use of chlorotrimethylsilane as an additive led to improved regio- and enantioselectivities.

ChemInform Abstract: Enantioselective Copper‐Catalyzed Allylic Alkylation of Cinnamyl Chlorides by Grignard Reagents Using Chiral Phosphine‐Phosphite Ligands.

ChemInformVolume 42, Issue 3 Preparative Organic Chemistry ChemInform Abstract: Enantioselective Copper-Catalyzed Allylic Alkylation of Cinnamyl Chlorides by Grignard Reagents Using Chiral Phosphine-Phosphite Ligands. Wibke Loelsberg, Wibke Loelsberg Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this authorShute Ye, Shute Ye Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this authorHans-Guenther Schmalz, Hans-Guenther Schmalz Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this author Wibke Loelsberg, Wibke Loelsberg Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this authorShute Ye, Shute Ye Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this authorHans-Guenther Schmalz, Hans-Guenther Schmalz Fachber. Chem., Univ. Koeln, D-50939 Koeln, GermanySearch for more papers by this author First published: 23 December 2010 https://doi.org/10.1002/chin.201103024Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume42, Issue3January 18, 2011 RelatedInformation

Phenol-derived chiral phosphine–phosphite ligands in the rhodium-catalyzed enantioselective hydrogenation of functionalized olefins

A set of 15 chiral Taddol- and Binol-based phosphine–phosphite ligands were tested in the Rh-catalyzed asymmetric hydrogenation of three olefins, methyl 2-hydroxymethyl-acrylate, 1-phenylvinyl acetate, and α-methyl cinnamic acid. The best enantioselectivities (up to 92% ee) were observed in the hydrogenation of methyl 2-hydroxymethyl-acrylate using Binol-based ligands. As previously observed in other applications of this class of modular chiral ligand in enantioselective catalysis, the stereochemical outcome of the reactions greatly depended on the substituents at the ligand aryl backbone in the ortho-position to the chiral phosphite unit.

ChemInform Abstract: New Chiral Phosphine-Phosphite Ligands in the Enantioselective Rhodium-Catalyzed Hydroformylation of Styrene.

ChemInform 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.

ChemInform Abstract: Chiral Phosphine—Phosphite Ligands in the Highly Enantioselective Rhodium‐Catalyzed Asymmetric Hydrogenation.

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.

New chiral phosphine-phosphite ligands in the enantioselective palladium-catalyzed allylic alkylation

A series of chiral phosphine-phosphite ligands 1-6 have been synthesized and used in the enantioselective palladium-catalyzed reaction of rac-1,3-diphenyl-2-propenyl acetate with dimethyl malonate as nucleophile. Ligands 1a, 2, 3, 5a, 6a, and 6b have been synthesized starting from racemic tert-butylphenylphosphinoborane. The use of dynamically resolved Li phosphide (-)-sparteine provided the optically pure ligands. Crystals of the allylpalladium (6a) complex were obtained, suitable for X-ray crystal structure determination. The X-ray crystal structure of the allylpalladium (6a) complex revealed a longer palladium-carbon bond distance trans to the phosphine moiety indicating that the attack of the nucleophile takes place at the carbon trans to the phosphine moiety. This was confirmed by the fact that the phosphine moiety did not affect the enantioselectivity directly. Under mild reaction conditions, enantioselectivities up to 83% were obtained (25 degrees C) with ligand 1e. Systematic variation of the ligand bridge and the phosphite moiety showed that the configuration of the product is controlled by the atropisomerism of the biphenyl substituent at the phosphite moiety. The conformation of the biphenyl group, in turn, is controlled by the substituent at the chiral carbon in the bridge. Ligands with large bite angles yielded higher enantioselectivities.

ChemInform Abstract: Enantioselective Hydroformylation of Olefins Catalyzed by Rhodium(I) Complexes of Chiral Phosphine—Phosphite Ligands

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.

Enantioselective hydroformylation of olefins catalyzed by rhodium(I) complexes of chiral phosphine–phosphite ligands

Using Rh(I) complexes of chiral phosphine–phosphites, hydroformylation of such a variety of olefins as aryl–substituted, alkyl–substituted, and heteroatom–substituted ones proceeded in high enantioselectivity. A trigonal bipyramidal RhH(CO)2(phosphine–phosphite) complex is suggested as the active species, in which the hydride and the phosphite moiety are located at the apical positions.