钯配合物催化的芳基-芳基不对称偶联反应

本文以三种匀性膦作配体制成了零价钯配合物, 并分虽试验了由它们催化苯酚得到的α-溴-β-苄氧基萘和进一步衍生而得的格氏试剂的偶联反应, 制成了β'β'-二苄氧基-α', α'-联萘.     

An efficient enantioselective fluorination of various beta-ketoesters catalyzed by chiral palladium complexes

Reflecting the importance of fluorinated organic compounds in medicinal chemistry, development of an efficient method for catalytic enantioselective fluorination is increasingly desirable. Using a novel palladium complex 2 (1-2.5 mol %), various beta-ketoesters including cyclic and acyclic substrates were fluorinated with excellent enantioselectivity in the range of 83-94% ee. It is environmentally advantageous that this reaction proceeds well in solvents such as EtOH, rather than usual organic solvents. Furthermore, the product was successfully tranformed into both alpha-fluoro beta-hydroxy and beta-amino acid derivatives, which should be extremely useful in developing novel drugs.     

手性膦过渡金属配合物催化不对称交叉偶联反应的研究

自1973年Consiglio和Botteghi首次报道用(一)-DIOP的NiCl_2配合物催化芳基或乙烯基卤代物与仲烷基卤化镁交叉偶联生成光学活性的偶联产物以来,化学家们对不对称交叉偶联反应进行了深入研究。Hayashi等用手性二茂铁膦和手性β-氨基烷基膦的NiCl_2和PdCl_2配合物催化1-苯基乙基氯化     

Highly efficient Suzuki-Miyaura coupling reactions catalyzed by bis(oxazolinyl)phenyl-Pd(II) complex

Bis(oxazolinyl)phenyl-palladium(II)(Phebox-Pd) complexes were found to be efficient catalysts for Suzuki-Miyaura coupling reactions of aryl boronic acids and their derivatives with aryl halides to give the corresponding biaryl products in high yield along with moderate enantioslectivities in the case of axially chiral induction. The catalytic activity was attained more than 900,000 of TON and 45,000 of TOF. The catalyst can be recovered quantitatively and could be reused for Suzuki-Miyaura reactions.     

Suzuki-Miyaura coupling catalyzed by polymer-incarcerated palladium, a highly active, recoverable, and reusable Pd catalyst

[reaction: see text] Suzuki-Miyaura coupling using a highly efficient and reusable polymer-incarcerated palladium (PI Pd) is described. Various coupling reactions proceeded smoothly using PI Pd with phosphine ligands, and the catalyst could be recovered by simple filtration and reused several times without loss of activity.     

Enantioselective pinacol coupling reaction of aromatic aldehydes catalyzed by chiral vanadium complexes

The asymmetric pinacol coupling of aromatic aldehydes by chiral salan–vanadium complexes as effective catalysts is reported. Chiral 1,2-diols were obtained with high diastereoselectivities (up to 90/10) and moderate to high enantioselectivities (up to 82% ee). The possible mechanism of the pinacol coupling reaction is also discussed.     

Convenient and efficient Suzuki-Miyaura cross-coupling catalyzed by a palladium/diazabutadiene system

[structure: see text]. A Pd(OAc)2/diazabutadiene system has been developed for the catalytic cross-coupling of aryl halides with arylboronic acids. A combination of the diazabutadiene DAB-Cy (1, N,N'-dicyclohexyl-1,4-dizabutadiene) and Pd(OAc)2 was found to form an excellent catalyst for the Suzuki-Miyaura cross-coupling of various aryl bromides and activated aryl chlorides with arylboronic acids.     

Efficient chiral monophosphorus ligands for asymmetric Suzuki-Miyaura coupling reactions

A series of novel P-chiral monophosphorus ligands exhibit efficiency in asymmetric Suzuki-Miyaura coupling reactions, enabling the construction of an array of chiral biaryl products in high yields and excellent enantioselectivities (up to 96% ee) under mild conditions. The carbonyl-benzooxazolidinone moiety in these chiral biaryl products allows facile derivatization for further synthetic applications. A computational study has revealed that a π-π interaction between the two coupling partners can enhance the enantioselectivity of the coupling reaction.     

Microwave-assisted aqueous Suzuki coupling reactions catalyzed by ionic palladium(II) complexes

Suzuki coupling is one of the most powerful methods for the synthesis of biaryls. We have prepared and characterized a series of unsymmetrical sulfonated water-soluble Pd(II)-pyridyl imine complexes and investigated them as catalysts for the Suzuki cross-coupling reaction in water under microwave irradiation. The compounds proved to be effective catalysts.     

A highly efficient kinetic resolution of Morita-Baylis-Hillman adducts achieved by N-Ar axially chiral Pd-complexes catalyzed asymmetric allylation

Palladium complexes with an axially chiral N-Ar framework have been developed. These complexes showed high stereoselectivities in asymmetric allylic arylation to achieve the kinetic resolution of Morita-Baylis-Hillman adducts, affording up to 99% ee of (E)-allylation products and 92% ee of recovered Morita-Baylis-Hillman adducts.     

New chiral scandium(III)/bisimine and diol complexes catalyzed asymmetric Diels-Alder reaction

Several bisimine and diol-based chiral ligands were examined as scandium(III) triflate complexes in the asymmetric Diels-Alder reaction of cyclopentadiene (2) with 3-acryloyloxazolidin-2-one (1) in the presence of 2,6-lutidine: the scandium/salen complex was revealed to be the most effective catalyst, which afforded the endo adduct in a good yield with 85% ee. Addition of a tertiary amine, such as 2,6-lutidine, was critical to achieve high enantioselectivity; enantioselectivity was remarkably decreased in the absence of the amine.     

Practical synthesis of 6-aryluridines via palladium(II) acetate catalyzed Suzuki-Miyaura cross-coupling reaction

Sugar-protected 6-halouridine derivatives underwent Suzuki-Miyaura cross-coupling reactions with arylboronic acids in the presence of palladium(II) acetate as a catalyst, triphenylphosphine as a ligand, and sodium carbonate as a base. This methodology is applicable to both the C5- and C6-position of uridine and provides a direct access for versatile uridine derivatives.     

Enantioselective Baeyer-Villiger oxidation catalyzed by palladium(II) complexes with chiral P,N-ligands

Asymmetric Baeyer-Villiger reaction of symmetrical cyclobutanones 1a-j with urea-hydrogen peroxide (UHP) can be catalyzed by a complex of Pd(II) and the new terpene-derived P, N-ligand 7. The resulting lactones 2a-j were obtained in high yields and with good enantioselectivity (< or =81% ee).     

Practical asymmetric Henry reaction catalyzed by a chiral diamine-Cu(OAc)2 complex

The chiral diamine ligand 3 was designed and synthesized from (R,R)-1,2-diphenylethylenediamine, (S)-2,2'-dibromomethyl-1,1'-binaphthalene, and o-xylylene dibromide. The resulting 3-Cu(OAc)2 complex was a highly efficient catalyst for the Henry reaction, giving the various nitroaldols with over 90% ee (up to >99%). The reaction was performed in n-propyl alcohol at room temperature, and the Henry adducts were produced in high yield with excellent enantiomeric excess; these attributes are desirable in a catalyst for practical use.     

Catalytic asymmetric coupling of 2-naphthols by chiral tridentate oxovanadium (IV) complexes

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted and N-3,4-benzo- and N-5,6-benzo-salicylidene-alpha-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O(2). The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-1-naphthaldehyde and valine (or phenylalanine) in CCl(4), leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.     

Enantioselective pinacol coupling of aryl aldehydes catalyzed by chiral Salan-Mo(IV) complexes

Reported herein is the asymmetric pinacol coupling of aromatic aldehydes with chiral Salan-Mo(VI) dioxo complex as an effective precatalyst. Chiral diols were obtained with high diastereoselectivity and enantioselectivity up to 92/8 and 95%, respectively. The possible mechanism of the pinacol coupling reaction with the catalytic system was investigated. The X-ray crystal structure of the precatalyst Mo(L3)O2 was determined and the oxidation state of the intermediate C was confirmed as +4 with X-ray photoelectron spectroscopy study. The proposed mechanism speculated the stereochemical outcome of the reaction, and a working model for the radical coupling of E was proposed, which explained the absolute configuration of the favored (S,S)-enantiomer of the dl isomer.     

Solid-supported palladium nano and microparticles: an efficient heterogeneous catalyst for ligand-free Suzuki-Miyaura cross coupling reaction

Solid-supported nano and microparticles of Pd(0) (SS-Pd) were prepared and used as heterogeneous catalysts for Suzuki-Miyaura cross coupling reactions of aryl halides (chloro, bromo and iodo) and phenyl boronic acid under mild and ligand-free conditions. Scanning electron microscope (SEM) and UV-vis based studies were performed to observe the distribution of nano and microparticles of palladium over solid surface and their oxidation states. In addition, the catalyst could be reused up to seven runs without significant loss of activity and stable enough under moist conditions.     

Triphenylphosphine chalcogenides as efficient ligands for room temperature palladium(II)-catalyzed Suzuki-Miyaura reaction

A simple catalytic system based on PdCl₂ and triphenylphosphine chalcogenides (PPh₃X; X = O, S, Se) is found to be highly effective (up to 97% isolated yield) in the room temperature Suzuki-Miyaura reactions. Under the same experimental conditions, triphenylphosphine chalcogenides as ligands show superior activities compared to free triphenylphosphine.