Gold‐Catalysed Oxyarylation of Styrenes and Mono‐ and gem‐Disubstituted Olefins Facilitated by an Iodine(III) Oxidant

1‐Hydroxy‐1,2‐benziodoxol‐3(1H)‐one (IBA) is an efficient terminal oxidant for gold‐catalysed, three‐component oxyarylation reactions. The use of this iodine(III) reagent expands the scope of oxyarylation to include styrenes and gem‐disubstituted olefins, substrates that are incompatible with the previously reported Selectfluor‐based methodology. Diverse arylsilane coupling partners can be employed, and in benzotrifluoride, homocoupling is substantially reduced. In addition, the IBA‐derived co‐products can be recovered and recycled.     

A TEMPO‐Free Copper‐Catalyzed Aerobic Oxidation of Alcohols

The copper‐catalyzed aerobic oxidation of primary and secondary alcohols without an external N‐oxide co‐oxidant is described. The catalyst system is composed of a Cu/diamine complex inspired by the enzyme tyrosinase, along with dimethylaminopyridine (DMAP) or N‐methylimidazole (NMI). The Cu catalyst system works without 2,2,6,6‐tetramethyl‐l‐piperidinoxyl (TEMPO) at ambient pressure and temperature, and displays activity for un‐activated secondary alcohols, which remain a challenging substrate for catalytic aerobic systems. Our work underscores the importance of finding alternative mechanistic pathways for alcohol oxidation, which complement Cu/TEMPO systems, and demonstrate, in this case, a preference for the oxidation of activated secondary over primary alcohols.     

Functionalized Periodic Mesoporous Organosilica: A Highly Enantioselective Catalyst for the Michael Addition of 1,3‐Dicarbonyl Compounds to Nitroalkenes

A functionalized periodic mesoporous organosilica with incorporated chiral bis(cyclohexyldiamine)‐based Ni^II complexes within the silica framework was developed by the co‐condensation of (1R,2R)‐cyclohexyldiamine‐derived silane and ethylene‐bridge silane, followed by the complexation of NiBr₂ in the presence of (1R,2R)‐N,N′‐dibenzylcyclohexyldiamine. Structural characterization by XRD, nitrogen sorption, and TEM disclosed its orderly mesostructure, and FTIR and solid‐state NMR spectroscopy demonstrated the incorporation of well‐defined single‐site bis(cyclohexyldiamine)‐based Ni^II active centers within periodic mesoporous organosilica. As a chiral heterogeneous catalyst, this functionalized periodic mesoporous organosilica showed high catalytic activity and excellent enantioselectivity in the asymmetric Michael addition of 1,3‐dicarbonyl compounds to nitroalkenes, comparable to those with homogeneous catalysts. In particular, this heterogeneous catalyst could be recovered easily and reused repeatedly up to nine times without obviously affecting its enantioselectivity, thus showing good potential for industrial applications.     

Asymmetric Hydroalkoxylation of Non‐Activated Alkenes: Titanium‐Catalyzed Cycloisomerization of Allylphenols at High Temperatures

The asymmetric catalytic addition of alcohols (phenols) to non‐activated alkenes has been realized through the cycloisomerization of 2‐allylphenols to 2‐methyl‐2,3‐dihydrobenzofurans (2‐methylcoumarans). The reaction was catalyzed by a chiral titanium–carboxylate complex at uncommonly high temperatures for asymmetric catalytic reactions. The catalyst was generated by mixing titanium isopropoxide, the chiral ligand (aS)‐1‐(2‐methoxy‐1‐naphthyl)‐2‐naphthoic acid or its derivatives, and a co‐catalytic amount of water in a ratio of 1:1:1 (5 mol % each). This homogeneous thermal catalysis (HOT‐CAT) gave various (S)‐2‐methylcoumarans with yields of up to 90 % and in up to 85 % ee at 240 °C, and in 87 % ee at 220 °C.     

Direct Regiospecific and Highly Enantioselective Intermolecular α‐Allylic Alkylation of Aldehydes by a Combination of Transition‐Metal and Chiral Amine Catalysts

The first direct intermolecular regiospecific and highly enantioselective α‐allylic alkylation of linear aldehydes by a combination of achiral bench‐stable Pd⁰ complexes and simple chiral amines as co‐catalysts is disclosed. The co‐catalytic asymmetric chemoselective and regiospecific α‐allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2‐alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2‐alkyl substituted hemiacetals, 2‐alkyl‐butane‐1,4‐diols, and amines. The concise co‐catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed.     

Chiral N‐Heterocyclic Carbene Ligands Bearing a Pyridine Moiety for the Copper‐Catalyzed Alkylation of N‐Sulfonylimines with Dialkylzinc Reagents

Amino acid‐derived chiral imidazolium salts, each bearing a pyridine ring, were developed as N‐heterocyclic carbene ligands. The copper‐catalyzed asymmetric alkylation of various N‐sulfonylimines with dialkylzinc reagents in the presence of these chiral imidazolium salts afforded the corresponding alkylated products with high enantioselectivity (up to 99 % ee). The addition of HMPA to the reaction mixture as a co‐solvent is critical in terms of chemical yield and enantioselectivity. A wide range of N‐sulfonylimines and dialkylzinc reagents were found to be applicable to this reaction.     

Access to P‐ and Axially Chiral Biaryl Phosphine Oxides by Enantioselective CpxIrIII‐Catalyzed C−H Arylations

An enantioselective C?H arylation of phosphine oxides with o‐quinone diazides catalyzed by an iridium(III) complex bearing an atropchiral cyclopentadienyl (Cp^x) ligand and phthaloyl tert‐leucine as co‐catalyst is reported. The method allows access to a) P‐chiral biaryl phosphine oxides, b) atropo‐enantioselective construction of sterically demanding biaryl backbones, and also c) selective assembly of axial and P‐chiral compounds in excellent yields and diastereo‐ and enantioselectivities. Enantiospecific reductions provide monodentate chiral phosphorus(III) compounds having structures and biaryl backbones with proven importance as ligands in asymmetric catalysis.     

Fast and clean dechlorination of alkyl and aryl (poly)chlorides catalysed by bimetallic Ni–Al clusters in the presence of t‐BuOH

The dechlorination of alkyl and aryl (poly)chlorides is rapid and complete upon treatment with a new reduction system consisting of NaH as reagent, Ni–Al clusters as catalyst and t‐BuOH as catalytic co‐factor. The high efficiency of this combination is presumed to be due to the stabilization of the subnanometre nickel particles formed during reduction by the in‐situ‐generated alkoxide. Copyright © 2001 John Wiley & Sons, Ltd.     

A Cinchona Alkaloid‐Functionalized Mesostructured Silica for Construction of Enriched Chiral β‐Trifluoromethyl‐β‐Hydroxy Ketones over An Epoxidation‐Relay Reduction Process

A cinchona alkaloid‐functionalized heterogeneous catalyst is prepared through a thiol‐ene click reaction of chiral N‐(3,5‐ditrifluoromethylbenzyl)quininium bromide and a mesostructured silica, which is obtained by co‐condensation of 1,2‐bis(triethoxysilyl)ethane and 3‐(triethoxysilyl)propane‐1‐thiol. Structural analyses and characterizations disclose its well‐defined chiral single‐site active center, and electron microscopy images reveal its monodisperse property. As a heterogenous catalyst, it enables an efficient asymmetric epoxidation of achiral β‐trifluoromethyl‐β,β‐disubstituted enones, the obtained chiral products can then be converted easily into enriched chiral β‐trifluoromethyl‐β‐hydroxy ketones through a sequential epoxidation‐relay reduction process. Furthermore, such a heterogeneous catalyst can be recovered conveniently and reused in asymmetric epoxidation of 4,4,4‐trifluoro‐1,3‐diphenylbut‐2‐enone, showing an attractive feature in a practical construction of enriched chiral β‐CF₃‐substituted molecules.     

Dual‐Mesoporous ZSM‐5 Zeolite with Highly b‐Axis‐Oriented Large Mesopore Channels for the Production of Benzoin Ethyl Ether

Dual‐mesoporous ZSM‐5 zeolite with highly b axis oriented large mesopores was synthesized by using nonionic copolymer F127 and cationic surfactant CTAB as co‐templates. The product contains two types of mesopores—smaller wormlike ones of 3.3 nm in size and highly oriented larger ones of 30–50 nm in diameter along the b axis—and both of them interpenetrate throughout the zeolite crystals and interconnect with zeolite microporosity. The dual‐mesoporous zeolite exhibits excellent catalytic performance in the condensation of benzaldehyde with ethanol and greater than 99 % selectivity for benzoin ethyl ether at room temperature, which can be ascribed to the zeolite lattice structure offering catalytically active sites and the hierarchical and oriented mesoporous structure providing fast access of reactants to these sites in the catalytic reaction. The excellent recyclability and high catalytic stability of the catalyst suggest prospective applications of such unique mesoporous zeolites in the chemical industry.     

Pd/Cu‐Catalyzed Enantioselective Sequential Heck/Sonogashira Coupling: Asymmetric Synthesis of Oxindoles Containing Trifluoromethylated Quaternary Stereogenic Centers

An asymmetric palladium and copper co‐catalyzed Heck/Sonogashira reaction between o‐iodoacrylanilides and terminal alkynes to synthesize chiral oxindoles was developed. In particular, a wide range of CF₃‐substituted o‐iodoacrylanilides reacted with terminal alkynes, affording the corresponding chiral oxindoles containing trifluoromethylated quaternary stereogenic centers in high yields with excellent enantioselectivities (94–98 % ee). This asymmetric Heck/Sonogashira reaction provides a general approach to access oxindole derivatives containing quaternary stereogenic centers including CF₃‐substituted ones.     

Asymmetric Synthesis of trans‐β‐Lactams by a Kinugasa Reaction on Water

The asymmetric Kinugasa reaction was performed on pure water for the first time without the need for any organic co‐solvents. In contrast to most asymmetric Kinugasa reactions, trans‐β‐lactams were obtained as the major products in good yields, enantioselectivities, and diastereoselectivities (up to 90 % yield, 98 % ee, and >99:1 d.r.). This reaction is atom‐economical, environmentally friendly, and affords synthetically useful but challenging products.     

Zirconium‐chelate and mono‐η‐ cyclopentadienyl zirconium‐chelate/ methylalumoxane systems as soluble Ziegler–Natta olefin polymerization catalysts

Zirconium‐chelate and mono‐η‐cyclopentadienyl zirconium‐chelate complexes were tested as ethene and propene polymerization catalysts in combination with methylalumoxane (MAO) as a co‐catalyst: in particular (acac) _nZrCl_4−n (1a–c) (acac = acetylacetonato), (dbm) _nZrCl_4−n (2a–2c) (dbm = dibenzoylmethanato = 1,3‐diphenylpropanedionato) (n = 2–4) and (dbm)₂ZrCl₂(thf) (3) (thf = tetrahydrofuran), (η‐C₅H₅)[H₂B (C₃H₃N₂)₂]ZrCl₂ (4), (η‐C₅H₅)[HB (C₃H₃N₂)₃] ZrCl₂ (5) and (η‐C₅H₅)[(Me₃SiN)₂ CPh]ZrCl₂ (6). Polymerization productivities comparable with the (η‐C₅H₅)₂ZrCl₂ reference system were observed towards ethene for all of the above complexes. In addition, compound 6 showed some minor polymerization activity towards propene. Ethylalumoxane or isobutylalumoxane did not exhibit a co‐catalytic activity for these chelate complexes; in combination with MAO these higher alumoxanes were even found to be deactivating ⁹¹Zr NMR data are reported for 1b, 1c, 4 and 5. Copyright © 2000 John Wiley & Sons, Ltd.     

Axial base‐controlled catalytic activity,oxidative stability and product selectivity of water‐insoluble manganese and iron porphyrins for oxidation of styrenes in water under green conditions

A series of water‐insoluble iron(III) and manganese(III) porphyrins, FeT(2‐CH₃)PPCl, FeT(4‐OCH₃)PPCl, FeT(2‐Cl)PPCl, FeTPPCl, MnT(2‐CH₃)PPOAc, MnT(4‐OCH₃)PPOAc, MnT(2‐Cl)PPOAc and MnTPPOAc, in the presence of imidazole (ImH), F^?, Cl^?, Br^? and acetate were used as catalysts for the aqueous‐phase heterogeneous oxidation of styrenes to the corresponding epoxides and aldehydes with sodium periodate. Also, the effect of various reaction parameters such as reaction time, molar ratio of catalyst to axial base, type of axial base, molar ratio of olefin to oxidant and nature of metal centre on the activity and oxidative stability of the catalysts and the product selectivity was investigated. Higher catalytic activities were found for the iron complexes. Interestingly, the selectivity towards the formation of epoxide and aldehyde (or acetophenone) was significantly influenced by the type of axial base. Furthermore, Br^? and ImH were found to be the most efficient co‐catalysts for the oxidation of olefins performed in the presence of the manganese and iron porphyrins, respectively. The optimized molar ratio of catalyst to axial base was different for various axial bases. Also, the order of co‐catalyst activity of the axial bases obtained in aqueous medium was different from that reported for organic solvents. The use of a convenient axial base under optimum reaction catalyst to co‐catalyst molar ratio in the presence of the manganese porphyrin gave the oxidative products with a conversion of ca 100% in a reaction time of less than 3 h. However, the catalytic activity of the iron porphyrins could not be effectively improved by increasing the catalyst to co‐catalyst molar ratio.     

Spontaneous Emergence of S‐Adenosylmethionine and the Evolution of Methylation

S ‐Adenosylmethionine (SAM) is an essential methylation cofactor. The origins of SAM methylation are complex, seemingly demanding the simultaneous emergence of an enzyme that makes SAM and enzyme(s) that utilize it. We report that both ATP and adenosine spontaneously react with methionine to yield SAM, thus suggesting that SAM could have emerged by chance. SAM methylation thus exemplifies how metabolites and pathways can co‐emerge through the gradual recruitment of individual enzymes in reverse order.     

Nitrogen,Phosphorus, and Sulfur Co‐Doped Hollow Carbon Shell as Superior Metal‐Free Catalyst for Selective Oxidation of Aromatic Alkanes

Metal‐free heteroatom‐doped carbocatalysts with a high surface area are desirable for catalytic reactions. In this study, we found an efficient strategy to prepare nitrogen, phosphorus, and sulfur co‐doped hollow carbon shells (denote as NPS‐HCS) with a surface area of 1020 m² g^?1. Using a poly(cyclotriphosphazene‐co‐4,4′‐sulfonyldiphenol) (PZS) shell as carbon source and N, P, S‐doping source, and the ZIF‐67 core as structural template as well as extra N‐doping source, NPS‐HCS were obtained with a high surface area and superhydrophilicity. All these features render the prepared NPS‐HCS a superior metal‐free carbocatalyst for the selective oxidation of aromatic alkanes in aqueous solution. This study provides a reliable and facile route to prepare doped carbocatalysts with enhanced catalytic properties.     

On the Mechanism of the Digold(I)–Hydroxide‐Catalysed Hydrophenoxylation of Alkynes

Herein, we present a detailed investigation of the mechanistic aspects of the dual gold‐catalysed hydrophenoxylation of alkynes by both experimental and computational methods. The dissociation of [{Au(NHC)}₂(μ‐OH)][BF₄] is essential to enter the catalytic cycle, and this step is favoured by the presence of bulky, non‐coordinating counter ions. Moreover, in silico studies confirmed that phenol does not only act as a reactant, but also as a co‐catalyst, lowering the energy barriers of several transition states. A gem‐diaurated species might form during the reaction, but this lies deep within a potential energy well, and is likely to be an “off‐cycle” rather than an “in‐cycle” intermediate.     

Chirally Functionalized Hollow Nanospheres Containing L‐Prolinamide: Synthesis and Asymmetric Catalysis

Chirally functionalized hollow nanospheres with different surface properties were successfully synthesized by co‐condensation of (2S,1′R,2′R)‐N‐tert‐butyloxycarbonylpyrrolidine‐2‐carboxylic acid [2′‐(4‐trimethoxysilylbenzylamide)cyclohexyl] amide with 1,2‐bis(trimethoxysilyl)ethane or tetramethoxysilane using F127 (EO₁₀₆PO₇₀EO₁₀₆) as surfactant in water. The TEM and N₂ sorption characterizations show that the particle size of the hollow nanosphere is 15–21 nm with a core diameter of 10–16 nm. These L ‐prolinamide‐functionalized hollow nanospheres are highly efficient solid catalysts for the direct asymmetric aldol reaction between cyclohexanone and aromatic aldehydes. It was found that the addition of water in the reaction system not only enhanced the catalytic activity but also increased the enantioselectivity, which is probably due to the enhanced hydrogen bond between the amide oxygen atom and the hydroxyl group of water. Moreover, the catalytic activity increases sharply as the surface hydrophobicity of the hollow nanospheres increases. These hollow nanospheres are quite stable and can be reused with almost the same enantioselectivity and only a slight decrease in catalytic activity.     

Chiral Mesoporous Organosilica Nanospheres: Effect of Pore Structure on the Performance in Asymmetric Catalysis

(R)‐(+)‐1,1′‐Bi‐2‐naphthol ((R)‐(+)‐Binol)‐functionalized (Binol=2,2′‐dihydroxy‐1,1′‐binaphthyl) chiral mesoporous organosilica nanospheres with uniform particle size (100 to 300 nm) have been synthesized by co‐condensation of tetraethoxysilane and (R)‐2,2′‐di(methoxymethyl)oxy‐6,6′‐di(1‐propyl trimethoxysilyl)‐1,1′‐binaphthyl in a basic medium with cetyltrimethylammonium bromide as the template. Nanospheres with a radiative 2D hexagonal channel arrangement exhibit higher enantioselectivity and turnover frequency than those with a penetrating 2D hexagonal channel arrangement (94 versus 88 % and 43 versus 15 h^?1, respectively) in the asymmetric addition of diethylzinc to aldehydes. In addition, under similar conditions, the enantioselectivity of the nanospheres can be greatly improved as the structural order of the framework increases. These results clearly show that the structural order of nanospheres affects enantioselective reactions. The enantioselectivity of the nanospheres synthesized by the co‐condensation method is higher than that of nanospheres prepared by a grafting method and even higher than that of their homogeneous counterpart. These results indicate that the bite angle of (R)‐(+)‐Binol bridging in a more rigid porous network is in a more favorable position for achieving higher enantioselectivity. The efficiency of a co‐condensation method for the synthesis of high‐performance heterogeneous asymmetric catalysts is also reported.     

One‐Pot Synthesis of Zeolitic Strong Solid Bases: A Family of Alkaline‐Earth Metal‐Containing Silicalite‐1

Fabricating stable strong basic sites in well‐preserved crystallized zeolitic frameworks still remains a difficult issue. Here, we reported a family of MFI‐type metallosilicate zeolites, AeS‐1 (Ae: alkaline‐earth metal ions of Mg, Ca, Sr or Ba; S‐1: silicalite‐1) through a direct one‐pot hydrothermal method involving the acidic co‐hydrolysis/condensation of the silica precursor with the Ae salts. Step‐by‐step full characterizations were designed and conducted for in‐depth discussion of the Ae status in AeS‐1. Strong basicity (H_≈22.5–26.5) was detected in AeS‐1. The basicity was further confirmed by CO₂ sorption measurements, ¹³C NMR spectra of chloroform‐adsorbed samples, and ¹H→¹³C and ¹H→²⁹Si cross‐polarization magic‐angle spinning NMR spectra of ethyl cyanoacetate‐adsorbed samples. The results of Knoevenagel condensations demonstrated the excellent solid base catalysis of AeS‐1, which showed high activity, reusability, and shape‐selectivity, all of which are explained by Ae‐derived zeolitic intracrystalline strong basic sites.