Application of phosphine-oxazoline ligands in Ir-catalyzed asymmetric hydrogenation of acyclic aromatic N-arylimines

[reaction: see text] A new class of chiral phosphine-oxazoline ligands have been developed. Chiral Ir complexes prepared from these ligands induced high enantioselectivities (66-90% ee) when applied to the asymmetric hydrogenation of acyclic aromatic N-arylimines.     

Palladium-catalyzed 1,4-addition of diarylphosphines to α,β-unsaturated N-acylpyrroles

Highly stereoselective asymmetric 1,4-addition of diarylphosphines to α,β-unsaturated N-acylpyrroles catalyzed by a PCP pincer-Pd complex has been developed for the synthesis of chiral phosphines with excellent stereoselectivity (91-99% ee) under mild conditions. The products obtained can be further converted into chiral phosphine-oxazoline ligands.     

Phosphine-oxazoline ligands with an axial-unfixed biphenyl backbone: the effects of the substituent at oxazoline ring and P phenyl ring on Pd-catalyzed asymmetric allylic alkylation

A novel kind of chiral phosphine-oxazoline ligands 3 with an axial-unfixed biphenyl backbone bearing different substituent on oxazoline ring and P phenyl ring was prepared. These ligands exist as a mixture of two diastereomers in equilibrium in solution. Upon coordinated to Pd(II), however, only one of the two possible kinds of diastereomer complexes with different axial chirality was formed. These compounds as chiral ligands were applied in Pd-catalyzed asymmetric allylic alkylation with high reaction activity and enantioselectivity. Meanwhile, the asymmetric catalytic behavior was affected obviously by the substituent at oxazoline ring and P phenyl ring. The best result, up to 92.3% ee and 99% yield, was obtained with the ligand 3c having two phenyl groups on P and a phenyl group on oxazoline ring in this asymmetric catalysis reaction.     

Iridium-catalyzed asymmetric hydrogenation of 3-substituted unsaturated oxindoles to prepare C3-mono substituted oxindoles

An efficient and enantioselective hydrogenation of 3-substituted unsaturated oxindoles has been developed by an iridium complex of tropos phosphine-oxazoline ligands. It is the first example to prepare chiral C3-mono substituted oxindoles via asymmetric catalysis. And the reaction provides instant access to this kind of compounds with excellent conversion and enantioselectivities (up to 93% ee).     

Enantioselective Hydroarylation of Olefins Using Palladium/Chiral Quinoline Oxazolines

Palladium-catalyzed arylation and alkenylation of olefins, known as the Heck reaction, is one of the most efficient catalytic methods for carbon-carbon bond formation in organic synthesis^[1]. During the last decade, asymmetric Heck reactions have attracted great attention, and a number of highly enantioselective chiral ligands have been developed to enhance chiral discrimination in these reactions^[2]. However, asymmetric Heck-type hydroarylations of olefins, addition of aryl halides or triflates to carbon-carbon double bonds, have not been well studied. In 1991, Brunner reported an asymmetric hydroarylation of norbornene and norbornadiene with aryl iodides using chiral bisphosphine ligands, and around 40% ee was achieved^[3]. Later on, Achiwa reached around 70% ee in the asymmetric hydroarylation of norbornene with phenyl triflate by using chiral P-N ligands^[4,5]. Herein, we wish to describe our investigations on chiral quinolinyl-oxazoline ligands that provide the first examples of efficient bisnitrogen ligands in Heck-type hydroarylation and the application of this reaction in the asymmetric synthesis of Epibatidine.     

Synthesis of 7,7’-Disubstituted BINAP and Their Application in Asymmetric Catalytic Reaction

The design of new chiral ligands plays a very important role in the development of transition metal catalyzed asymmetric synthesis. Many chiral diphosphine ligands have been prepared and applied in asymmetric catalytic reactions with excellent enantioselectivities. Among the chiral diphosphine ligands reported, BINAP was found to have been the widest application in the transition metal catalyzed reaction. Recently we have developed a novel oxovanadium (Ⅳ) complex catalyst for the oxidative …     

Synthesis of new bicyclic P-N ligands and their application in asymmetric Pd-catalyzed pi-allyl alkylation and Heck reaction

[structure: see text] The synthesis of phosphine oxazoline ligands based on P-chiral 1-phosphanorbornadienes is reported. The use of these ligands in palladium catalyzed asymmetric allylation and Heck reaction is described.     

StePHOX, a new family of optically active, tunable phosphine-oxazoline ligands: syntheses and applications

A new class of optically active phosphine-oxazoline ligands has been synthesized wherein backbone chirality of these new ligands is installed by a Sharpless asymmetric dihydroxylation. Different backbone protecting groups as well as different substitution patterns on the oxazoline ring were studied. These ligands were tested in allylic substitution (with ee's up to 97%) and asymmetric Tsuji allylation.     

A highly enantioselective intramolecular Heck reaction with a monodentate ligand.

An efficient enantioselective intramolecular Heck reaction of cyclohexadienones, using readily available and modular TADDOL-based mono- and bidentate phosphoramidites as chiral ligands and not requiring any additives, has been developed. Excellent enantioselectivities up to 96% ee are reached for the first time in a Heck reaction with monodentate ligands.     

Asymmetric hydrogenation of aromatic olefins catalyzed by iridium complexes of proline derived phosphine-oxazoline ligands

The synthesis of a series of phosphine-oxazoline ligands is reported. This ligands are synthesized by reaction of a phosphine chloride with the secondary nitrogen of proline. Upon coordination to iridium the resulting complexes can be used in the asymmetric hydrogenation of simple olefins. The effect of different counter ions and substitution at the oxazoline and the phosphine is reported.     

Enantioselective synthesis of P-stereogenic benzophospholanes via palladium-catalyzed intramolecular cyclization

Enantioselective or diastereoselective intramolecular cyclization of functionalized secondary phosphines or their borane adducts catalyzed by chiral Pd(diphosphine) complexes gave P-stereogenic benzophospholanes in up to 70% ee. These results provide a new method for the synthesis of chiral phospholanes, which are valuable ligands in asymmetric catalysis. [reaction: see text]     

AraBOX and XyliBOX based catalysts for cyclopropanations,Diels Alder cycloadditions and allylic additions

The syntheses of three novel chiral 4,4′BOX ligands are described. The three ligands each have a chiral backbone and chiral sidearms, two of which are diastereomeric. These new ligands have been applied as copper complexes to asymmetric cyclopropanation reaction of styrene with ethyldiazoacetate. Enantioselectivities of up to 70% were obtained, which is the highest ee reported from the use of this ligand class in this reaction to date. The multiple stereogenic centres in the ligand resulted in a substantial additive effect and this is discussed along with interpretation of the results for previously described 4,4′BOX ligands, and a major computational study of the multiple reaction channels involved with ligands of this type. The use of complexes of 4,4′BOX ligands, as catalysts, in an allylic alkylation is also reported for the first time and ee’s of >70% have been achieved in this reaction. These ligands were also applied to a Diels–Alder test reaction and again outperformed previous examples of this ligand type.     

轴不安定性联苯类膦-噁唑啉配体/铱配合物在亚胺不对称氢化反应中的应用

考察了一系列轴不安定性联苯类膦-噁唑啉配体/铱配合物作为手性催化剂用于亚胺类底物的不对称催化氢化反应.结果表明该类催化剂具有很高的催化活性(99%转化率)和较好的对映选择性(75%ee).     

手性二茂铁类配体在钯催化不对称反应中的应用

本文综述了近10 年来手性二茂铁类配体在钯催化不对称烯丙基取代反应,包括各种不同底物的烯丙基烷基化、烯丙基胺基化和烯丙基磺酰化反应中的应用,并对其在不对称Claisen 重排、不对称Diels-Alder 反应、不对称Heck 反应、不对称羰基化、不对称氢化硅烷化和不对称碳碳键断裂等反应中的应用进行了综述,对部分反应的机理和该领域的发展前景进行了讨论。     

Enantioselective Iron‐Catalyzed Intramolecular Cyclopropanation Reactions

An iron‐catalyzed asymmetric intramolecular cyclopropanation was realized in high yields and excellent enantioselectivity (up to 97 % ee) by using the iron complexes of chiral spiro‐bisoxazoline ligands as catalysts. The superiority of iron catalysts exhibited in this reaction demonstrated the potential abilities of this sustainable metal in asymmetric carbenoid transformation reactions.     

Axially chiral phosphine-oxazoline ligands in silver(I)-catalyzed asymmetric Mannich reaction of N-Boc aldimines with trimethylsiloxyfuran

Axially chiral phosphine-oxazoline ligand L6 was found to be a fairly effective chiral ligand in silver(I)-catalyzed asymmetric Mannich reaction of N-Boc aldimines with trimethylsiloxyfuran to give the corresponding adducts in up to 97% yield, 7:1 dr and 86% ee (major diastereoisomer).     

Mixed S/P Ligands from Carbohydrates: Synthesis and Utilization in Asymmetric Catalysis

Abstract

New chiral mixed sulfur/phosphorus ligands derived from carbohydrates are reported. These ligands were found to be efficient catalyst precursors for palladium-catalyzed asymmetric substitution of 1,3-diphenylpropenyl acetate with dimethyl malonate or benzylamine (up to 96% ee), and for rhodium-catalyzed methyl acetamidocinnamate hydrogenation (up to 92% ee).     

镍催化硅基保护烯丙醇的烯氢化反应:一种合成含有手性季碳中心高烯丙醇的有效方法

报道了一例手性螺环亚磷酰胺配体和镍的络合物催化的硅基保护烯丙醇的不对称烯氢化反应,以较高的收率(最高达97%)和对映选择性(最高达95%ee)合成了一系列含有手性季碳中心的高烯丙醇.该反应为含有手性季碳中心的双官能团化合物的合成提供了新的有效方法.     

A short and concise asymmetric synthesis of hamigeran B

The interesting biological properties of the hamigerans wherein hamigeran B is a potent antiviral agent with low cytotoxicity to host cells make these deceptively simple looking structures challenging synthetic targets. A strategy to hamigeran B evolved wherein the three contiguous stereocenters are established ultimately from a Pd catalyzed asymmetric allylic alkylation (AAA). The latter involves an asymmetric allylation of a non-stabilized ketone enolate in 77 % yield and 93 % ee. By using this process, (S)-5-allyl-2-isopropyl-5-methyl-1-trifluoromethanesulfonyloxycyclopentene becomes available in four steps from 2-methylcyclopentanone. Introduction of the aryl unit by cross-coupling proceeded intermolecularly but failed intramolecularly. On the other hand, reductive removal of the triflate permitted a Heck reaction to effect intramolecular introduction of the aryl ring. The unusual conformational properties of this molecular architecture are revealed by the regioselectivity of the beta-hydrogen elimination in the Heck reaction and the diastereoselectivity of the reduction establishing the stereochemistry of the carbon bearing the isopropyl group. The successful route consists of 15 steps from 2-methylcyclopentanone and dimethylorcinol illustrating the efficiency of the route based upon the Pd AAA.     

Enantioselective Rh-catalyzed hydrogenation of N-formyl dehydroamino esters with monodentate phosphoramidite ligands

Enantioselectivities up to >99% ee were achieved in the rhodium-catalyzed asymmetric hydrogenation of N-formyl dehydroamino esters using monodentate phosphoramidites as chiral ligands. The substrates were synthesized by condensation of methyl isocyanoacetate with a range of aldehydes and with cyclohexanone. A highly convenient multigram scale one step synthesis of methyl 2-(formamido)acrylate was developed. This compound was used in the synthesis of methyl 2-(formamido)cinnamate via a solvent free Heck reaction. Moreover, full conversion and >99% ee were obtained in 1 h in the hydrogenation of methyl 2-(formamido)acrylate with 0.2 mol % catalyst and 2 bar hydrogen pressure. The versatility of the formyl protection was established by its removal under mild conditions.