不对称合成中手性磷配体催化剂的研究进展 (Ⅱ) (续完)

评述了作为配体催化剂的手性三配位及四配位磷化合物的合成及其在某些不对称合成反应中的应用     

The AZARYPHOS Family of Ligands for Ambifunctional Catalysis: Syntheses and Use in Ruthenium‐Catalyzed anti‐Markovnikov Hydration of Terminal Alkynes

The family of AZARYPHOS (aza–aryl–phosphane) phosphane ligands, containing a phosphine unit and sterically shielded nitrogen lone pairs in the ligand periphery, is introduced as a tool for developing ambifunctional catalysis by the metal center and nitrogen lone pairs in the ligand sphere. General synthetic strategies have been developed to synthesize over 25 examples of structurally diverse (6‐aryl‐2‐pyridyl)phosphanes (ARPYPHOS), (6‐alkyl‐2‐pyridyl)phosphanes (ALPYPHOS), 4,6‐disubsituted 1,3‐diazin‐2‐ylphosphanes or 1,3,5‐triazin‐2‐ylphosphanes, quinazolinylphosphanes, quinolinylphosphanes, and others. The scalable syntheses proceed in a few steps. The incorporation of AZARYPHOS ligands ( L ) into complexes [RuCp( L )₂(MeCN)][PF₆] (Cp=cyclopentadienyl) gives catalysts for the anti‐Markovnikov hydration of terminal alkynes of the highest known activities. Electronic and steric ligand effects modulate the reaction kinetics over a range of two orders of magnitude. These results highlight the importance of using structurally diverse ligand families in the process of developing cooperative ambifunctional catalysis by a metal and its ligand.     

The Versatility of Tertiary Phosphane Ligands in Coordination and Organometallic Chemistry

Tertiary phosphanes form kinetically stable complexes with formal oxidation states of the metal ranging from + IV to ?I (“electronic versatility”). Variously substituted phosphanes and polydentate, chelate forming phosphanes and polyphosphanes can be synthesized (“steric versatility”). Studies on complexes containing such ligands provide, inter alia, useful information about the metal-phosphorus bond, about the steric effects of the phosphane ligand, and about reactions of coordinated phosphanes.     

不对称合成中手性磷配体催化剂的研究进展(Ⅰ)(待续)

评述了作为配体催化剂的手性三配位及四配位磷化合物的合成及其在某些不对称的合反应中的应用     

Chiral Amino Acids‐Derived Catalysts and Ligands

Transforming amino acids into novel catalysts and ligands is a remarkable subset of new catalyst development in order to imitate enzymatic efficiencies. Their ability to perform a variety of asymmetric catalytic reactions is complimented by their ready availability, rich transformations, stability and easy procedure. Herein, we focused on describing our endeavor of developing new catalysts and ligands from primary and secondary amino acids. It includes C₂‐symmetric N,N'‐dioxides, guanidine‐amides, bispidine‐based diamines, and other organic salts. The account covered a brief introduction about their discovery, representative applications and related mechanisms.     

Phosphorus Heterocycles: From Laboratory Curiosities to Ligands in Highly Efficient Catalysts

Phosphabenzenes and phosphaferrocenes were among the first compounds with P−C multiple bonds. For nearly 30 years the chemistry of these molecules was essentially a domain left to basic researchers. Recently, however, it was reported that transition metal complexes with phosphabenzene and phosphaferrocene ligands exhibit remarkable potential as catalysts. Catalysts based on rhodium (I ) and various phosphabenzenes appear to be superior to classical systems in the hydroformylation of terminal and internal alkenes. In addition planar‐chiral phosphaferrocene species display an excellent performance as directing ligands in a series of enantioselective asymmetric syntheses.     

New Ligands for Regio- and Enantiocontrol in Pd-Catalyzed Allylic Alkylations

The branched, chiral products 1 are formed preferentially in the allylic alkylations in Equation (1) when the Pd catalyst contains the P,N ligand L* or derivatives thereof. The ligands are readily synthesized from commercially available precursors.     

Facile and Efficient Reduction of Ketones in the Presence of Zinc Catalysts Modified by Phenol Ligands

In the present study, the zinc‐catalyzed hydrosilylation of various ketones to give their corresponding alcohols has been examined in detail. Diethyl zinc that can be modified by easily accessible phenol ligands allows the efficient reduction of various aryl and alkyl ketones. By using a practical in situ catalyst, excellent turnover frequencies up to 1000 h^?1 and a broad functional group tolerance were achieved.     

Enantioselective Addition of Diethylzinc to Benzaldehyde by Catalysts of Chiral Heterocyclic Ligands

TheenantioselectiveadditionofdiethylzincreagentstoprochiralcarbonylgrouphasbeenachievedprincipallybycatalyticalamountofchiralP-aminoalcoholswhichhaveproventobehighlyeffectivecatalysts'.Ahydroxylgrouphasbeenregardedtobenecessaryforthechiralligandtoformazincalkoxideasthecatalyticspecies'.Wewishtoreporthereinontheethylationofbenzaldehydewithdiethylzincpromotedbyseveralkindsofoxazolidineandthiazolidinederivativeswhichdonotcontainhydroxylgroup.Fourkindschiralheterocyclicligandsweusedarelistedasfoll…     

Monometallic Ni0 and Heterobimetallic Ni0/AuI Complexes of Tripodal Phosphine Ligands: Characterization in Solution and in the Solid State and Catalysis

The tridentate chelate nickel complexes [(CO)Ni{(PPh₂CH₂)₃CMe}] ( 2 ), [(CO)Ni{(PPh₂CH₂CH₂)₃SiMe}] ( 6 ), and [Ph₃PNi{(PPh₂CH₂CH₂)₃SiMe}] ( 7 ), as well as the bidentate complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂PPh₂}] ( 3 ) and the heterobimetallic complex [(CO)₂Ni{(PPh₂CH₂)₂CMeCH₂Ph₂PAuCl}] ( 4 ), have been synthesized and fully characterized in solution. All ¹H and ¹³C NMR signal assignments are based on 2D‐NMR methods. Single crystal X‐ray structures have been obtained for all complexes. Their ³¹P CP/MAS (cross polarization with magic angle spinning) NMR spectra have been recorded and the isotropic lines identified. The signals were assigned with the help of their chemical shift anisotropy (CSA) data. All complexes have been tested regarding their catalytic activity for the cyclotrimerization of phenylacetylene. Whereas complexes 2 – 4 display low catalytic activity, complex 7 leads to quantitative conversion of the substrate within four hours and is highly selective throughout the catalytic reaction.     

Alkyl,Silyl, and Phosphane Ligands—Classical Ligands in Nonclassical Bonding Modes

Alkyl, silyl, and phosphane ligands are amongst the most familiar and ubiquitous ligands in organometallic and coordination chemistry. The C, Si, and P donor atoms of these ligands are sp³‐hybridized and the ligands are related to each other by the isolobal analogy: (CR₃)−(SiR₃)−PR₃. Herein, we demonstrate that although a number of unusual observations concerning the reactivity and bonding of these ligands appears unrelated at first sight, they in fact provide offer an exiting and consistent picture that may form the basis for new paradigms. The characterization of stable complexes in which alkyl, silyl, and phosphane ligands behave as symmetrical bridges confirms that there is no inherent thermodynamic instability associated with these bonding situations, and, in fact, reactivity studies suggest that these ligands should be able to bridge between metal centers in reaction intermediates or transition states.     

New benzo[h]quinoline-based ligands and their pincer Ru and Os complexes for efficient catalytic transfer hydrogenation of carbonyl compounds

New benzo[h]quinoline ligands (HCN'N) containing a CHRNH2 (R=H (a), Me (b), tBu (c)) function in the 2-position were prepared starting from benzo[h]quinoline N-oxide (in the case of ligand a) and 2-chlorobenzo[h]quinoline (for ligands b and c). These compounds were used to prepare ruthenium and osmium complexes, which are excellent catalysts for the transfer hydrogenation (TH) of ketones. The reaction of a with [RuCl2(PPh3)3] in 2-propanol at reflux afforded the terdentate CN'N complex [RuCl(CN'N)(PPh3)2] (1), whereas the complexes [RuCl(CN'N)(dppb)] (2-4; dppb=Ph2P(CH2)4PPh2) were obtained from [RuCl2(PPh3)(dppb)] with a-c, respectively. Employment of (R,S)-Josiphos, (S,R)-Josiphos*, (S,S)-Skewphos, and (S)-MeO-Biphep in combination with [RuCl2(PPh3)3] and ligand a gave the chiral derivatives [RuCl(CN'N)(PP)] (5-8). The osmium complex [OsCl(CN'N)(dppb)] (12) was prepared by treatment of [OsCl2(PPh3)3] with dppb and ligand a. Reaction of the chloride 2 and 12 with NaOiPr in 2-propanol/toluene afforded the hydride complexes [MH(CN'N)(dppb)] (M=Ru 10, Os 14), through elimination of acetone from [M(OiPr)(CN'N)(dppb)] (M=Ru 9, Os 13). The species 9 and 13 easily reacted with 4,4'-difluorobenzophenone, via 10 and 14, respectively, affording the corresponding isolable alkoxides [M(OR)(CN'N)(dppb)] (M=Ru 11, Os 15). The complexes [MX(CN'N)(P2)] (1-15) (M=Ru, Os; X=Cl, H, OR; P=PPh3 and P2=diphosphane) are efficient catalysts for the TH of carbonyl compounds with 2-propanol in the presence of NaOiPr (2 mol %). Turnover frequency (TOF) values up to 1.8x10(6) h(-1) have been achieved using 0.02-0.001 mol % of catalyst. Much the same activity has been observed for the Ru--Cl, --H, --OR, and the Os--Cl derivatives, whereas the Os--H and Os--OR derivatives display significantly lower activity on account of their high oxygen sensitivity. The chiral Ru complexes 5-8 catalyze the asymmetric TH of methyl-aryl ketones with TOF approximately 10(5) h(-1) at 60 degrees C, up to 97 % enatiomeric excess (ee) and remarkably high productivity (0.005 mol % catalyst loading). High catalytic activity (TOF up to 2.2x10(5) h(-1)) and enantioselectivity (up to 98 % ee) have also been achieved with the in-situ-generated catalysts prepared from [MCl2(PPh3)3], (S,R)-Josiphos or (S,R)-Josiphos*, and the benzo[h]quinoline ligands a-c.     

Chiral and Nonchiral [OsX2(diphosphane)(diamine)] (X: Cl,OCH2CF3) Complexes for Fast Hydrogenation of Carbonyl Compounds

The osmium complexes trans‐[OsCl₂(dppf)(diamine)] (dppf: 1,1′‐bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3 , propylenediamine in 4 ) were prepared by the reaction of [OsCl₂(PPh₃)₃] ( 1 ) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH₂CF₃ in toluene afforded the alkoxide cis‐[Os(OCH₂CF₃)₂(dppf)(ethylenediamine)] ( 5 ). The novel precursor [Os₂Cl₄(P(m‐tolyl)₃)₅] ( 2 ) allows the synthesis of the chiral complexes trans‐[OsCl₂(diphosphane)(1,2‐diamine)] ( 6 – 9 ; diphosphane: (R)‐[6,6′‐dimethoxy(1,1′‐biphenyl)‐2,2′‐diyl]bis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylMeObiphep) or (R)‐(1,1′‐binaphthalene)‐2,2′‐diylbis[1,1‐bis(3,5‐dimethylphenyl)phosphane] (xylbinap); diamine=(R,R)‐1,2‐diphenylethylenediamine (dpen) or (R,R)‐1,2‐diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2‐diamine in toluene at reflux temperature. Compounds 3 – 5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H₂ at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10 000–200 000 and achieving turnover frequencies (TOFs) of up to 3.0×10⁵ h^?1 at 70 °C. By employment of the chiral compounds 6 – 9 , different ketones, including alkyl aryl, bulky tert‐butyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99 % and with S/C ratios of 5000–100 000 and TOFs of up to 4.1×10⁴ h^?1 at 60 °C.     

Pincer and diamine Ru and Os diphosphane complexes as efficient catalysts for the dehydrogenation of alcohols to ketones

The ruthenium and osmium complexes [MCl₂(diphosphane)(L)] (M=Ru, Os; L=bidentate amino ligand) and [MCl(CNN)(dppb)] (CNN=pincer ligand; dppb=1,4‐bis‐ (diphenylphosphino)butane), containing the N–H moiety, have been found to catalyze the acceptorless dehydrogenation of alcohols in tBuOH and in the presence of KOtBu. The compounds trans‐[MCl₂(dppf)(en)] (M=Ru 7 , Os 13 ; dppf=1,1′‐bis(diphenylphosphino)ferrocene; en=ethylenediamine) display very high activity and different substrates, including cyclic and linear alcohols, are efficiently oxidized to ketones by using 0.8–0.04 mol % of catalyst. The effect of the base and the comparison of the catalytic activity of the Ru versus Os complexes are reported. The ruthenium complex 7 generally leads to a faster conversion into ketones with respect to the osmium complex 13 , which displays better activity in the dehydrogenation of 5‐en‐3β‐hydroxy steroids. The synthesis of new Ru and Os complexes [MCl₂(PP)(L)] (PP=dppb, dppf; L=(±)‐trans‐1,2‐diaminocyclohexane, 2‐(aminomethyl)pyridine, and 2‐aminoethanol) of trans and cis configuration is also reported.     

p-Substituted Tris(2-pyridylmethyl)amines as Ligands for Highly Active ATRP Catalysts: Facile Synthesis and Characterization

A facile and efficient two-step synthesis of p-substituted tris(2-pyridylmethyl)amine (TPMA) ligands to form Cu complexes with the highest activity to date in atom transfer radical polymerization (ATRP) is presented. In the divergent synthesis, p-Cl substituents in tris(4-chloro-2-pyridylmethyl)amine (TPMA^3Cl) were replaced in one step and high yield by electron-donating cyclic amines (pyrrolidine (TPMA^PYR), piperidine (TPMA^PIP), and morpholine (TPMA^MOR)) by nucleophilic aromatic substitution. The [Cu^II(TPMA^NR2)Br]⁺ complexes exhibited larger energy gaps between frontier molecular orbitals and >0.2 V more negative reduction potentials than [Cu^II(TPMA)Br]⁺, indicating >3 orders of magnitude higher ATRP activity. [Cu^I(TPMA^PYR)]⁺ exhibited the highest reported activity for Br-capped acrylate chain ends in DMF, and moderate activity toward C−F bonds at room temperature. ATRP of n-butyl acrylate using only 10–25 part per million loadings of [Cu^II(TPMA^NR2)Br]⁺ exhibited excellent control.