- Anti-Markovnikov alkene oxidation by metal-oxo–mediated enzyme catalysis
-
Catalytic anti-Markovnikov oxidation of alkene feedstocks could simplify synthetic routes to many important molecules and solve a long-standing challenge in chemistry. Here we report the engineering of a cytochrome P450 enzyme by directed evolution to catalyze metal-oxo–mediated anti-Markovnikov oxidation of styrenes with high efficiency. The enzyme uses dioxygen as the terminal oxidant and achieves selectivity for anti-Markovnikov oxidation over the kinetically favored alkene epoxidation by trapping high-energy intermediates and catalyzing an oxo transfer, including an enantioselective 1,2-hydride migration. The anti-Markovnikov oxygenase can be combined with other catalysts in synthetic metabolic pathways to access a variety of challenging anti-Markovnikov functionalization reactions.
- Hammer, Stephan C.,Kubik, Grzegorz,Watkins, Ella,Huang, Shan,Minges, Hannah,Arnold, Frances H.
-
-
Read Online
- Improved Catalytic Activity and Stability of a Palladium Pincer Complex by Incorporation into a Metal-Organic Framework
-
A porous metal-organic framework Zr6O4(OH)4(L-PdX)3 (1-X) has been constructed from Pd diphosphinite pincer complexes ([L-PdX]4- = [(2,6-(OPAr2)2C6H3)PdX]4-, Ar = p-C6H4CO2-, X = Cl, I). Reaction of 1-X with PhI(O2CCF3)2 facilitates I-/CF3CO2- ligand exchange to generate 1-TFA and I2 as a soluble byproduct. 1-TFA is an active and recyclable catalyst for transfer hydrogenation of benzaldehydes using formic acid as a hydrogen source. In contrast, the homogeneous analogue tBu(L-PdTFA) is an ineffective catalyst owing to decomposition under the catalytic conditions, highlighting the beneficial effects of immobilization.
- Burgess, Samantha A.,Kassie, Abebu,Baranowski, Sarah A.,Fritzsching, Keith J.,Schmidt-Rohr, Klaus,Brown, Craig M.,Wade, Casey R.
-
-
Read Online
- On the intermolecular interaction of N-benzylquininium chloride or quinine with some carbonyl group containing compounds
-
Interactions between N-benzylquininium chloride (Quibec) and some carbonyl group containing compounds were investigated using 1H NMR and theoretical calculations. Results highlight the importance of the hydrogen bonding between the Quibec C-9 h
- Avila, Thais C.,Reginato, Marcelo M.,Di Vitta, Cláudio,Ducati, Lucas C.,Andrade, Leandro H.,Marzorati, Liliana
-
-
Read Online
- Catalyst Repurposing Sequential Catalysis by Harnessing Regenerated Prolinamide Organocatalysts as Transfer Hydrogenation Ligands
-
A catalyst repurposing strategy based on a sequential aldol addition and transfer hydrogenation giving access to enantiomerically enriched α-hydroxy-γ-butyrolactones is described. The combination of a stereoselective, organocatalytic step, followed by an efficient catalytic aldehyde reduction induces an ensuing lactonization to provide enantioenriched butyrolactones from readily available starting materials. By capitalizing from the capacity of prolineamides to act as both an organocatalyst and a transfer hydrogenation ligand, catalyst repurposing allowed the development of an operationally simple, economic, and efficient sequential catalysis approach.
- Bourgeois, Frederic,Medlock, Jonathan A.,Bonrath, Werner,Sparr, Christof
-
-
Read Online
- Copper-catalyzed enantioselective hydroboration of unactivated 1, 1-disubstituted alkenes
-
We report an efficient and highly enantioselective hydroboration of aliphatic 1, 1-disubstituted alkenes with pinacolborane using a phosphine-Cu catalyst. The method allows facile preparation of enantiomerically enriched β-chiral alkyl pinacolboronates from a range of 1, 1-disubstituted alkenes with high enantioselectivity up to 99% ee. Unprecedented enantiodiscrimination between the geminal alkyl substituents was observed with functional group compatibility in the hydroboration. Furthermore, a catalyst loading as low as 1 mol % furnished the desired product without a decrease in yield or selectivity, demonstrating its efficiency in gram scale synthesis.
- Jang, Won Jun,Song, Seung Min,Moon, Jong Hun,Lee, Jin Yong,Yun, Jaesook
-
-
Read Online
- Enantioselective Ir-catalyzed hydrogenation of minimally functionalized olefins using pyranoside phosphinite-oxazoline ligands
-
Pyranoside phosphinite-oxazoline ligands prepared from readily available (+)-D-glucosamine were applied to the Ir-catalyzed asymmetric hydrogenation of minimally functionalized olefins. Our results show that the enantioselectivity is dependent on the ozaxoline and the phosphinite moieties and the substrate structure. By carefully selecting the ligand components, enantioselectivities up to 99 % were obtained in the asymmetric reduction of several (E)- and (Z)-trisubstituted and 1,1-disubstituted olefins. The asymmetric hydrogenation was also performed using propylene carbonate as solvent, which allowed the iridium catalysts to be reused and maintained the high enantioselectivities. Copyright
- Mazuela, Javier,Pamies, Oscar,Dieguez, Montserrat
-
-
Read Online
- Vanadium hydrogen sulfate (I): Chemoselective trimethylsilylation of alcohols and deprotection of trimethylsilyl ethers
-
Trimethylsilylation of alcohols with hexamethyldisilazane (HMDS) catalyzed by V(HSO4)3 under mild and completely heterogeneous reaction condition is reported. The method is highly chemoselective for the protection of alcohols in the presence of phenols, amines and thiols. Also, the deprotection of trimethylsilyl ethers is performed in the presence of V(HSO 4)3 at room temperature in good to high yields.
- Shirini, Farhad,Zolfigol, Mohammad Ali,Abedini, Masoumeh,Sakhaei, Ali Reza
-
-
Read Online
- Regioselective methylation of the secondary carbinol center of prim, sec-diols
-
Reaction of 2-oxo-4-phenyl-1,3,2-dioxathiolane and 2-oxo-4-(tert- butyldiphenylsilylmethyl)-13,2-dioxathiolane with trimethylaluminium selectively took place at the secondary carbinol center to give 2-phenyl-1- propanol and 3-(tert-butyldiphenylsilyl)-2-methylpropanol. When the endo- or exo-isomer of (S)-2-oxo-4-phenyl-13,2-dioxathiolane reacted with trimethylaluminium, (R)-2-phenyl-1-propanol was obtained in 75% ee or 90% ee, respectively.
- Yoshida, Hifumi,Takada, Akinori,Mitsunobu, Oyo
-
-
Read Online
- Electronic effects in asymmetric hydroboration
-
To determine whether electronic effects are operative in asymmetric hydroboration, a series of para-substituted 2-aryl-1-propenes were prepared and reacted with four asymmetric borane reagents. A significant correlation between the electronic nature of the para-substituent and the degree of asymmetric induction was observed only for a chloroborane-ether complex, not for any of several simple alkylboranes. A quantitative analysis of the relative reactivities is also given.
- Garner, Charles M.,Chiang, Shirley,Nething, Matthew,Monestel, Robert
-
-
Read Online
- Four-Coordinated Manganese(II) Disilyl Complexes for the Hydrosilylation of Aldehydes and Ketones with 1,1,3,3-Tetramethyldisiloxane
-
The coordinatively unsaturated manganase(II) bis(supersilyl) complex Mn[Si(SiMe3)3]2(THF)2 (2) was synthesized in one step via the reaction of MnBr2 with two equivalents of KSi(SiMe3)3 in THF. Complex 2 acts as an effective precatalyst for the catalytic hydrosilylation of aldehydes and ketones with 1,1,3,3-tetramethyldisiloxane (TMDS). The catalytic efficiency can be improved by combining 2 and adamantyl isocyanide (CNAd). The stoichiometric reaction of 2 and two equivalents of CNAd led to the isolation of Mn[Si(SiMe3)3]2(CNAd)2 (3) in high yield. Complex 3 shows superior catalytic performance than 2 in the hydrosilylation of relatively unreactive ketones.
- Saito, Kyoka,Ito, Tatsuyoshi,Arata, Shogo,Sunada, Yusuke
-
-
Read Online
- Sustainable radical reduction through catalytic hydrogen atom transfer
-
A system with coupled catalytic cycles is described that allows radical reduction by hydrogen atom abstraction from rhodium hydrides. These intermediates are generated from H2 activation by Wilkinson's catalyst. Radical generation is carried out by titanocene-catalyzed electron transfer to epoxides. Copyright
- Gansaeuer, Andreas,Fan, Chun-An,Piestert, Frederik
-
-
Read Online
- Iminopyridine oxazoline iron catalyst for asymmetric hydroboration of 1,1-disubtituted aryl alkenes
-
The highly regio- and enantioselective iron-catalyzed anti-Markovnikov hydroboration of 1,1-disubstituted aryl alkenes is reported by using a novel chiral iminopyridine oxazoline (IPO) ligand, in which the iminopyridine group is proposed to stabilize the iron and chiral oxazoline group to control enantioselectivity. This distinct class of reactive IPO ligands will likely be of high value for a large variety of asymmetric transformations using first-row transition metals.
- Chen, Jianhui,Xi, Tuo,Lu, Zhan
-
-
Read Online
- Reductive coupling of carbonyl compounds to pinacols by using Sm-I2MeOH or Sm-I2-Ti(O(i)Pr)4-MeOH systems
-
The coupling reaction of aromatic carbonyl compounds was performed with Sm-I2 or Sm-I2-Ti(O(i)Pr)4 in methanol. Meso isomer was mainly produced in the presence of Ti(O(i)Pr4.
- Yanada, Reiko,Negoro, Nobuyuki,Yanada, Kazuo,Fujita, Tetsuro
-
-
Read Online
- A versatile approach to optically active primary 2-fluoro-2-phenylalkanols through lipase-catalyzed transformations
-
Kinetic resolutions of (+/-)-1-acetoxy-2-fluoro-2-phenylalkanes 1 by enzymatic hydrolysis and of (+/-)-2-fluoro-2-phenylpropanol 2a by lipase-catalyzed acetylation are described for the first time.Hydrolysis of (+/-)-1 with lipase Amano PS (Pseudomonas cepacia) provided both the optically active acetates (-)-1 and the corresponding primary alcohols (-)-2 with high enantiomeric excess. (R)-enantiopreference was observed for the acetylation of (+/-)-2-fluoro-2-phenylpropanol 2a which occurred with higher enantioselectivity and faster conversion compared to the unfluorinated parent compound (+/-)-2-phenylpropanol 3.
- Goj, Olav,Burchardt, Annegret,Haufe, Guenter
-
-
Read Online
- Biphasic hydroformylation in ionic liquids: Interaction between phosphane ligands and imidazolium triflate, toward an asymmetric process
-
Biphasic hydroformylation of dec-1-ene and styrene, at commercially competitive rates, can be successfully performed in imidazolium triflate ionic liquids; the ionic liquid network forms 'inclusion complexes' with the phosphane ligands used to modify the rhodium catalyst. The Royal Society of Chemistry.
- Leclercq, Loic,Suisse, Isabelle,Agbossou-Niedercorn, Francine
-
-
Read Online
- Organocatalytic Stereoselective Addition of Aldehydes to Acylquinolinium Ions
-
A direct and simple activation of quinolines, without isolating unstable intermediates, or using isolated N,O-acetals in the presence of Lewis or Br?nsted acids, is described. The procedure is quite straightforward and allows the addition in a stereoselective manner of different aldehydes to various differently substituted quinolines. The desired products were obtained in 28–76 % yields, with dr values up to 83:17 in favor of the syn isomer, and up to 99 % ee. Studies towards the use of acetaldehyde were also performed with different catalysts and the addition was promoted affording the desired product in 62 % yield with 46 % ee. Finally, deprotection and chemical transformations of the enantioenriched adducts were performed.
- Mengozzi, Luca,Gualandi, Andrea,Cozzi, Pier Giorgio
-
-
Read Online
- NICKEL-CATALYZED STEREODIFFERENTIATING DISPLACEMENT REACTION BETWEEN PROCHIRAL 1-ALKENES AND OPTICALLY ACTIVE ORGANOALUMINIUM SOLVATES.
-
The displacement reaction between optically active AlBui3 solvates and vinylidene alkenes, in the presence of Ni(mesal)2, affords optically active trialkylalanes and hence, upon hydrolysis or oxidative procedure, alkanes or 1-alkanols.
- Giacomelli, Giampaolo,Bertero, Luigi,Lardicci, Luciano
-
-
Read Online
- Synthesis of R-(-)-2-phenylpropanal: A potentially new route towards chiral 2-phenylalkanals
-
A facile two step synthesis of (R)-2-phenylpropanal in high enantiomeric excess is described, starting from commercial (S)-styrene oxide, involving as a key step a Dess-Martin oxidation.
- Botuha, Candice,Haddad, Mansour,Larcheveque, Marc
-
-
Read Online
- Homologations of boronate esters: the first observation of sequential insertions
-
By employing dibromo or diiodomethane as halomethyllithium precursors, the in situ double and triple homologation of boronate esters has been obtained for the first time.
- Ren, Li,Crudden, Cathleen M.
-
-
Read Online
- Visible-Light-Enhanced Cobalt-Catalyzed Hydrogenation: Switchable Catalysis Enabled by Divergence between Thermal and Photochemical Pathways
-
The catalytic hydrogenation activity of the readily prepared, coordinatively saturated cobalt(I) precatalyst, (R,R)-(iPrDuPhos)Co(CO)2H ((R,R)-iPrDuPhos = (+)-1,2-bis[(2R,5R)-2,5-diisopropylphospholano]benzene), is described. While efficient turnover was observed with a range of alkenes upon heating to 100 °C, the catalytic performance of the cobalt catalyst was markedly enhanced upon irradiation with blue light at 35 °C. This improved reactivity enabled hydrogenation of terminal, di-, and trisubstituted alkenes, alkynes, and carbonyl compounds. A combination of deuterium labeling studies, hydrogenation of alkenes containing radical clocks, and experiments probing relative rates supports a hydrogen atom transfer pathway under thermal conditions that is enabled by a relatively weak cobalt-hydrogen bond of 54 kcal/mol. In contrast, data for the photocatalytic reactions support light-induced dissociation of a carbonyl ligand followed by a coordination-insertion sequence where the product is released by combination of a cobalt alkyl intermediate with the starting hydride, (R,R)-(iPrDuPhos)Co(CO)2H. These results demonstrate the versatility of catalysis with Earth-abundant metals as pathways involving open-versus closed-shell intermediates can be switched by the energy source.
- Mendelsohn, Lauren N.,MacNeil, Connor S.,Tian, Lei,Park, Yoonsu,Scholes, Gregory D.,Chirik, Paul J.
-
-
Read Online
- Convenient method for preparing polystyrene having β-hydroxy group: Its application to the synthesis of polyethylene glycol-grafted polystyrene resin
-
An efficient method for preparing β-hydroxy polystyrene resin is described. Friedel-Crafts alkylation of polystyrene resin with propylene oxide in the of Lewis acid catalyst afford 2-(1-methyl) hydroxyethyl polystyrene (PS-PO). Addition of ethylene oxides to the PS PO in the presence of base gave presence PS-g-PEG resins. The resin contained 60-80%(w/w) of PEG and showed excellent stability in highly acidic media.
- Park, Byeong-Deog,Lee, Hyeong-Ik,Ryoo, Sun-Jong,Lee, Yoon-Sik
-
-
Read Online
- Deracemisation of profenol core by combining laccase/TEMPO-mediated oxidation and alcohol dehydrogenase-catalysed dynamic kinetic resolution
-
A mild one-pot methodology has been developed to deracemise rac-2-phenyl-1-propanol by combining the use of non-selective laccase/TEMPO-mediated oxidation with enantioselective bioreduction of the racemic aldehyde intermediate under dynamic conditions. The process was easily scalable and stereocontrollable by selecting the suitable biocatalyst.
- Díaz-Rodríguez, Alba,Ríos-Lombardía, Nicolás,Sattler, Johann H.,Lavandera, Iván,Gotor-Fernández, Vicente,Kroutil, Wolfgang,Gotor, Vicente
-
-
Read Online
- Regioselective Reduction of Epoxides by Electron Transfer-a Photochemical Approach
-
Irradiation of epoxides in the presence of amines and sodium borohydride leads cleanly to a regioselectively opening of the epoxide, giving the lesser substituted alcohol as a product.
- Epling, Gary A.,Wang, Qingxi
-
-
Read Online
- The development and evaluation of a conducting matrix for the electrochemical regeneration of the immobilised co-factor NAD(H) under continuous flow
-
Through the preparation of a novel controlled pore glass-poly(pyrrole) material we have developed a conducting support that is not only suitable for the co-immobilisation of enzymes and co-factors, but also enables the facile electrochemical regeneration of the co-factor during a reaction. Employing the selective reduction of (rac)-2-phenylpropionaldehyde to (S)-phenyl-1-propanol as a model, we have demonstrated the successful co-immobilisation of the HLADH enzyme and co-factor NAD(H); with incorporation of the material into a continuous flow reactor facilitating the in situ electrochemical regeneration of NAD(H) for in excess of 100 h. Using this approach we have developed a reagent-less, atom efficient system applicable to the cost-effective, continuous biosynthesis of chiral compounds.
- Ngamsom,Hickey,Greenway,Littlechild,McCreedy,Watts,Wiles
-
-
Read Online
- Diisopropoxyaluminium Trifluoroacetate: A New off the Shelf Metal Alkoxide Type Reducing Agent for Reduction of Aldehydes and Ketones
-
A new off the shelf reducing agent, diisopropoxyaluminium trifluoroacetate, has been prepared by reacting aluminium isopropoxide with trifluoroacetic acid in dichloromethane. It is a white solid and stable when stored under dry conditions. Using this reagent various aldehydes and ketones have been reduced to the corresponding alcohols in moderate to quantitative yields, at room temperature in short time.
- Akamanchi,Varalakshmy,Chaudhari
-
-
Read Online
- Catalytic asymmetric hydrogenation of aldehydes
-
Racemic α-arylaldehydes provide the corresponding primary alcohols via dynamic kinetic resolution in excellent enantioselectivities and yields upon hydrogenation using a Noyori ruthenium catalyst; for example, the biologically active (S)-enantiomer of the non-steroidal anti-inflammatory drug ibuprofen could be synthesized via catalytic enantioselective hydrogenation of aldehyde 1f followed by oxidation with potassium permanganate in 76% isolated yield and 96: 4 er. The Royal Society of Chemistry.
- Li, Xiaoguang,List, Benjamin
-
-
Read Online
- Structural Elucidation of the Mechanism of Molecular Recognition in Chiral Crystalline Sponges
-
To gain insight into chiral recognition in porous materials we have prepared a family of fourth generation chiral metal–organic frameworks (MOFs) that have rigid frameworks and adaptable (flexible) pores. The previously reported parent material, [Co2(S-mandelate)2(4,4′-bipyridine)3](NO3)2, CMOM-1S, is a modular MOF; five new variants in which counterions (BF4?, CMOM-2S) or mandelate ligands are substituted (2-Cl, CMOM-11R; 3-Cl, CMOM-21R; 4-Cl, CMOM-31R; 4-CH3, CMOM-41R) and the existing CF3SO3? variant CMOM-3S are studied herein. Fine-tuning of pore size, shape, and chemistry afforded a series of distinct host–guest binding sites with variable chiral separation properties with respect to three structural isomers of phenylpropanol. Structural analysis of the resulting crystalline sponge phases revealed that host–guest interactions, guest–guest interactions, and pore adaptability collectively determine chiral discrimination.
- Fairen-Jimenez, David,Zaworotko, Michael J.,Zhang, Shi-Yuan
-
-
Read Online
- Regioselective cleavage of epoxides. Conversion of racemic epoxides to optically active alcohols
-
Regioselective reduction of racemic epoxides to optically active alcohols using chirally modified zirconium tetrachloride - sodium borohydride with L-proline.
- Santosh Laxmi,Iyengar
-
-
Read Online
- Water/MAO acceleration of the zirconocene-catalyzed asymmetric methylalumination of α-olefins
-
(matrix presented) The zirconocene-catalyzed enantioselective methylalumination of terminal alkenes is greatly accelerated in the presence of water. Terminal olefins that are inert under the standard conditions can be readily methylated in good yields and with good to high enantioselectivities. Furthermore, methylaluminoxane is also shown to accelerate the reaction, albeit at a lesser rate.
- Wipf, Peter,Ribe, Seth
-
-
Read Online
- An Unusual Anti-Markovnikov Hydration of Alkenes with Titanium(III) Tetrahydroborates
-
Titanium(III) tetrahydroborate formed by the reaction of titanium tetrachloride and benzyltriethylammonium borohydride (1:4) reacts with alkenes in dichloromethane (-20 deg C) very readily to yield directly the corresponding alcohols in excellent yields after a simple aqueous work up.
- Kumar, K. S. Ravi,Baskaran, S.,Chandrasekaran, S.
-
-
Read Online
- Regioselective Reductive Cleavage of Terminal Epoxides with Polymer-supported Chloroaluminium Tetrahydroborate
-
Epoxides are reduced exclusively to the less substituted alcohols with regenerable polyvinylpyridine-supported chloroaluminium tetrahydroborate in high yields.
- Tamami, Bahman,Lakouraj, M. Mansour,Yeganeh, Hamid
-
-
Read Online
- Highly efficient asymmetric reduction of arylpropionic aldehydes by Horse Liver Alcohol Dehydrogenase through dynamic kinetic resolution
-
The enantioselective synthesis of (2S)-2-phenylpropanol and (2S)-2-(4-iso-butylphenyl)propanol ((S)-Ibuprofenol) has been achieved by means of Horse Liver Alcohol Dehydrogenase (HLADH) in buffered aqueous solution or buffered organic solvent mixtures; under the reaction conditions, a dynamic kinetic resolution (DKR) process was realized with good reaction yields and enantiomeric ratios. The Royal Society of Chemistry.
- Giacomini, Daria,Galletti, Paola,Quintavalla, Arianna,Gucciardo, Gabriele,Paradisi, Francesca
-
-
Read Online
- Asymmetric Reduction of Prochiral Ketones by Using Self-Sufficient Heterogeneous Biocatalysts Based on NADPH-Dependent Ketoreductases
-
The development of cell-free and self-sufficient biocatalytic systems represents an emerging approach to address more complex synthetic schemes under nonphysiological conditions. Herein, we report the development of a self-sufficient heterogeneous biocatalyst for the synthesis of chiral alcohols without the need to add an exogenous cofactor. In this work, an NADPH-dependent ketoreductase was primarily stabilized and further co-immobilized with NADPH to catalyze asymmetric reductions without the addition of an exogenous cofactor. As a result, the immobilized cofactor is accessible, and thus, it is recycled inside the porous structure without diffusing out into the bulk, as demonstrated by single-particle in operando studies. This self-sufficient heterogeneous biocatalyst was used and recycled for the asymmetric reduction of eleven carbonyl compounds in a batch reactor without the addition of exogenous NADPH to achieve the corresponding alcohols in 100 % yield and >99 % ee; this high performance was maintained over five consecutive reaction cycles. Likewise, the self-sufficient heterogeneous biocatalyst was integrated into a plug flow reactor for the continuous synthesis of one model secondary alcohol, which gave rise to a space-time yield of 97–112 g L?1 day?1; additionally, the immobilized cofactor accumulated a total turnover number of 1076 for 120 h. This is one of the few examples of the successful implementation of continuous reactions in aqueous media catalyzed by cell-free and immobilized systems that integrate both enzymes and cofactors into the solid phase.
- Benítez-Mateos, Ana I.,San Sebastian, Eneko,Ríos-Lombardía, Nicolás,Morís, Francisco,González-Sabín, Javier,López-Gallego, Fernando
-
-
Read Online
- Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
-
The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.
- De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey
-
p. 235 - 246
(2022/01/03)
-
- Integrated Experimental and Computational Studies on the Organocatalytic Kinetic Resolution of β-Unfunctionalized Primary Alcohols Using a Chiral 1,2-Diamine: The Importance of Noncovalent Interactions
-
The enantioselective kinetic resolution of β-unfunctionalized primary alcohols with benzoyl chloride was carried out in the presence of a catalytic amount of a novel chiral 1,2-diamine derived from (S)-proline. Several valuable chiral 2-substituted propan-1-ols were obtained with good enantioselectivities. Density functional theory calculations revealed that the noncovalent interaction, such as CH-πinteraction, is crucial for the enantioselectivity of the resolution. This study was conducted through an interplay between experiment and computation.
- Mori, Seiji,Ojima, Kohei,Oriyama, Takeshi,Sakai, Naoki
-
supporting information
p. 4468 - 4475
(2022/03/14)
-
- Epoxide Electroreduction
-
Selective hydrogenation of epoxides would be a direct and powerful approach for alcohol synthesis, but it has proven to be elusive. Here, electrochemically epoxide hydrogenation using electrons and protons as reductants is reported. A wide range of primary, secondary, and tertiary alcohols can be achieved through selective Markovnikov or anti-Markovnikov ring opening in the absence of transition metals. Mechanistic investigations revealed that the regioselectivity is controlled by the thermodynamic stabilities of the in situ generated benzyl radicals for aryl-substituted epoxides and the kinetic tendency for Markovnikov selective ring opening for alkyl-substituted epoxides.
- Huang, Cheng,Lu, Qingquan,Ma, Wan,Qi, Xiaotian,Xu, Minghao,Zheng, Xuelian
-
p. 1389 - 1395
(2022/01/19)
-
- Rhodium-Catalyzed Regiodivergent Synthesis of Alkylboronates via Deoxygenative Hydroboration of Aryl Ketones: Mechanism and Origin of Selectivities
-
Here, we report an efficient rhodium-catalyzed deoxygenative borylation of ketones to synthesize alkylboronates, in which the regioselectivity can be switched by the choice of the ligand. The linear alkylboronates were obtained exclusively in the presence of P(nBu)3, and PPh2Me favored the formation of branched alkylboronates. The protocol also allows access to 1,1,2-triboronates from the readily available ketones. Mechanistic studies suggest that this Rh-catalyzed deoxygenative borylation of ketones goes through an alkene intermediate, which undergoes regiodivergent hydroboration to afford linear and branched alkylboronates. The different steric effects of PPh2Me and P(nBu)3 were found to be responsible for product selectivity by density functional theory calculations. The alkene intermediate can alternatively undergo sequential dehydrogenative borylation and hydroboration to deliver the triboronates.
- Zhang, Bing,Xu, Xin,Tao, Lei,Lin, Zhenyang,Zhao, Wanxiang
-
p. 9495 - 9505
(2021/08/04)
-
- Combined Theoretical and Experimental Studies Unravel Multiple Pathways to Convergent Asymmetric Hydrogenation of Enamides
-
We present a highly efficient convergent asymmetric hydrogenation of E/Z mixtures of enamides catalyzed by N,P-iridium complexes supported by mechanistic studies. It was found that reduction of the olefinic isomers (E and Z geometries) produces chiral amides with the same absolute configuration (enantioconvergent hydrogenation). This allowed the hydrogenation of a wide range of E/Z mixtures of trisubstituted enamides with excellent enantioselectivity (up to 99% ee). A detailed mechanistic study using deuterium labeling and kinetic experiments revealed two different pathways for the observed enantioconvergence. For α-aryl enamides, fast isomerization of the double bond takes place, and the overall process results in kinetic resolution of the two isomers. For α-alkyl enamides, no double bond isomerization is detected, and competition experiments suggested that substrate chelation is responsible for the enantioconvergent stereochemical outcome. DFT calculations were performed to predict the correct absolute configuration of the products and strengthen the proposed mechanism of the iridium-catalyzed isomerization pathway.
- Yang, Jianping,Massaro, Luca,Krajangsri, Suppachai,Singh, Thishana,Su, Hao,Silvi, Emanuele,Ponra, Sudipta,Eriksson, Lars,Ahlquist, M?rten S. G.,Andersson, Pher G.
-
p. 21594 - 21603
(2021/12/27)
-
- Primary Alcohols via Nickel Pentacarboxycyclopentadienyl Diamide Catalyzed Hydrosilylation of Terminal Epoxides
-
The efficient and regioselective hydrosilylation of epoxides co-catalyzed by a pentacarboxycyclopentadienyl (PCCP) diamide nickel complex and Lewis acid is reported. This method allows for the reductive opening of terminal, monosubstituted epoxides to form unbranched, primary alcohols. A range of substrates including both terminal and nonterminal epoxides are shown to work, and a mechanistic rationale is provided. This work represents the first use of a PCCP derivative as a ligand for transition-metal catalysis.
- Lambert, Tristan H.,Steiniger, Keri A.
-
supporting information
p. 8013 - 8017
(2021/10/25)
-
- Tropylium-Promoted Hydroboration Reactions: Mechanistic Insights Via Experimental and Computational Studies
-
Hydroboration reaction of alkynes is one of the most synthetically powerful tools to access organoboron compounds, versatile precursors for cross-coupling chemistry. This type of reaction has traditionally been mediated by transition-metal or main group catalysts. Herein, we report a novel method using tropylium salts, typically known as organic oxidants and Lewis acids, to promote the hydroboration reaction of alkynes. A broad range of vinylboranes can be easily accessed via this metal-free protocol. Similar hydroboration reactions of alkenes and epoxides can also be efficiently catalyzed by the same tropylium catalysts. Experimental studies and DFT calculations suggested that the reaction follows an uncommon mechanistic pathway, which is triggered by the hydride abstraction of pinacolborane with tropylium ion. This is followed by a series ofin situcounterion-activated substituent exchanges to generate boron intermediates that promote the hydroboration reaction.
- Mai, Binh Khanh,Nguyen, Thanh Vinh,Ton, Nhan N. H.
-
p. 9117 - 9133
(2021/07/19)
-
- Reaction of Diisobutylaluminum Borohydride, a Binary Hydride, with Selected Organic Compounds Containing Representative Functional Groups
-
The binary hydride, diisobutylaluminum borohydride [(iBu)2AlBH4], synthesized from diisobutylaluminum hydride (DIBAL) and borane dimethyl sulfide (BMS) has shown great potential in reducing a variety of organic functional groups. This unique binary hydride, (iBu)2AlBH4, is readily synthesized, versatile, and simple to use. Aldehydes, ketones, esters, and epoxides are reduced very fast to the corresponding alcohols in essentially quantitative yields. This binary hydride can reduce tertiary amides rapidly to the corresponding amines at 25 °C in an efficient manner. Furthermore, nitriles are converted into the corresponding amines in essentially quantitative yields. These reactions occur under ambient conditions and are completed in an hour or less. The reduction products are isolated through a simple acid-base extraction and without the use of column chromatography. Further investigation showed that (iBu)2AlBH4 has the potential to be a selective hydride donor as shown through a series of competitive reactions. Similarities and differences between (iBu)2AlBH4, DIBAL, and BMS are discussed.
- Amberchan, Gabriella,Snelling, Rachel A.,Moya, Enrique,Landi, Madison,Lutz, Kyle,Gatihi, Roxanne,Singaram, Bakthan
-
supporting information
p. 6207 - 6227
(2021/05/06)
-
- Green pepper aroma compound as well as preparation method and application thereof
-
The invention relates to the technical field of spices, in particular to a green pepper aroma compound as well as a preparation method and application thereof. The green pepper aroma compound is a novel aroma raw material, has the following structural formula, has special green pepper aroma, is accompanied with green aroma and bay leaf aroma, is high in molecular weight, not easy to volatilize and lasting in aroma, and can be used as a fixative.
- -
-
Paragraph 0070; 0075-0077; 0089; 0094-0096
(2021/05/08)
-
- Copper-catalyzed hydroformylation and hydroxymethylation of styrenes
-
Hydroformylation catalyzed by transition metals is one of the most important homogeneously catalyzed reactions in industrial organic chemistry. Millions of tons of aldehydes and related chemicals are produced by this transformation annually. However, most of the applied procedures use rhodium catalysts. In the procedure described here, a copper-catalyzed hydroformylation of alkenes has been realized. Remarkably, by using a different copper precursor, the aldehydes obtained can be further hydrogenated to give the corresponding alcohols under the same conditions, formally named as hydroxymethylation of alkenes. Under pressure of syngas, various aldehydes and alcohols can be produced from alkenes with copper as the only catalyst, in excellent regioselectivity. Additionally, an all-carbon quaternary center containing ethers and formates can be synthesized as well with the addition of unactivated alkyl halides. A possible reaction pathway is proposed based on our results. This journal is
- Franke, Robert,Geng, Hui-Qing,Meyer, Tim,Wu, Xiao-Feng
-
p. 14937 - 14943
(2021/12/02)
-
- Ru-Catalyzed Selective Catalytic Methylation and Methylenation Reaction Employing Methanol as the C1 Source
-
Methanol can be employed as a green and sustainable methylating agent to form C-C and C-N bonds via borrowing hydrogen (BH) methodology. Herein we explored the activity of the acridine-derived SNS-Ru pincer for the activation of methanol to apply it as a C1 building block in different reactions. Our catalytic system shows great success toward the β-C(sp3)-methylation reaction of 2-phenylethanols to provide good to excellent yields of the methylated products. We investigated the mechanistic details, kinetic progress, and temperature-dependent product distribution, which revealed the slow and steady generation of in situ formed aldehyde, is the key factor to get the higher yield of the β-methylated product. To establish the environmental benefit of this reaction, green chemistry metrics are calculated. Furthermore, dimerization of 2-naphthol via methylene linkage and formation of N-methylation of amine are also described in this study, which offers a wide range of substrate scope with a good to excellent yield.
- Biswas, Nandita,Srimani, Dipankar
-
p. 10544 - 10554
(2021/07/31)
-
- Carbon monoxide and hydrogen (syngas) as a C1-building block for selective catalytic methylation
-
A catalytic reaction using syngas (CO/H2) as feedstock for the selective β-methylation of alcohols was developed whereby carbon monoxide acts as a C1 source and hydrogen gas as a reducing agent. The overall transformation occurs through an intricate network of metal-catalyzed and base-mediated reactions. The molecular complex [Mn(CO)2Br[HN(C2H4PiPr2)2]]1comprising earth-abundant manganese acts as the metal component in the catalytic system enabling the generation of formaldehyde from syngas in a synthetically useful reaction. This new syngas conversion opens pathways to install methyl branches at sp3carbon centers utilizing renewable feedstocks and energy for the synthesis of biologically active compounds, fine chemicals, and advanced biofuels.
- Kaithal, Akash,H?lscher, Markus,Leitner, Walter
-
p. 976 - 982
(2021/02/06)
-
- Highly efficient NHC-iridium-catalyzed β-methylation of alcohols with methanol at low catalyst loadings
-
The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups. Here, a highly efficient β-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium (bis-NHC-Ir) complexes. Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products. The protocol was readily extended to the β-alkylation of alcohols with several primary alcohols. Control experiments, along with DFT calculations and crystallographic studies, revealed that the ligand effect is critical to their excellent catalytic performance, shedding light on more challenging Guerbet reactions with simple alcohols. [Figure not available: see fulltext.].
- Lu, Zeye,Zheng, Qingshu,Zeng, Guangkuo,Kuang, Yunyan,Clark, James H.,Tu, Tao
-
p. 1361 - 1366
(2021/06/30)
-
- Selective Production of Linear Aldehydes and Alcohols from Alkenes using Formic Acid as Syngas Surrogate
-
Performing carbonylation without the use of carbon monoxide for high-value-added products is an attractive yet challenging topic in sustainable chemistry. Herein, effective methods for producing linear aldehydes or alcohols selectively with formic acid as both carbon monoxide and hydrogen source have been described. Linear-selective hydroformylation of alkenes proceeds smoothly with up to 88 % yield and >30 regioselectivity in the presence of single Rh catalyst. Strikingly, introducing Ru into the system, the dual Rh/Ru catalysts accomplish efficient and regioselective hydroxymethylation in one pot. The present processes utilizing formic acid as syngas surrogate operate simply under mild condition, which opens a sustainable way for production of linear aldehydes and alcohols without the need for gas cylinders and autoclaves. As formic acid can be readily produced via CO2 hydrogenation, the protocols represent indirect approaches for chemical valorization of CO2.
- Chen, Junjun,Hua, Kaimin,Liu, Xiaofang,Deng, Yuchao,Wei, Baiyin,Wang, Hui,Sun, Yuhan
-
p. 9919 - 9924
(2021/05/31)
-
- Regiodivergent Hydroborative Ring Opening of Epoxides via Selective C-O Bond Activation
-
A magnesium-catalyzed regiodivergent C-O bond cleavage protocol is presented. Readily available magnesium catalysts achieve the selective hydroboration of a wide range of epoxides and oxetanes yielding secondary and tertiary alcohols in excellent yields and regioselectivities. Experimental mechanistic investigations and DFT calculations provide insight into the unexpected regiodivergence and explain the different mechanisms of the C-O bond activation and product formation.
- Magre, Marc,Paffenholz, Eva,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
-
supporting information
p. 14286 - 14294
(2020/09/15)
-
- A General Regioselective Synthesis of Alcohols by Cobalt-Catalyzed Hydrogenation of Epoxides
-
A straightforward methodology for the synthesis of anti-Markovnikov-type alcohols is presented. By using a specific cobalt triphos complex in the presence of Zn(OTf)2 as an additive, the hydrogenation of epoxides proceeds with high yields and selectivities. The described protocol shows a broad substrate scope, including multi-substituted internal and terminal epoxides, as well as a good functional-group tolerance. Various natural-product derivatives, including steroids, terpenoids, and sesquiterpenoids, gave access to the corresponding alcohols in moderate-to-excellent yields.
- Beller, Matthias,Junge, Kathrin,Leischner, Thomas,Li, Wu,Liu, Weiping
-
supporting information
p. 11321 - 11324
(2020/05/16)
-
- Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
-
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
- Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
-
p. 13659 - 13667
(2020/11/30)
-
- Styrene Hydroformylation with In Situ Hydrogen: Regioselectivity Control by Coupling with the Low-Temperature Water–Gas Shift Reaction
-
The hydroformylation of olefins is one of the most important homogeneously catalyzed industrial reactions for aldehyde synthesis. Various ligands can be used to obtain the desired linear aldehydes in the hydroformylation of aliphatic olefins. However, in the hydroformylation of aromatic substrates, branched aldehydes are formed preferentially with common ligands. In this study, a novel approach to selectively obtain linear aldehydes in the hydroformylation of styrene and its derivatives was developed by coupling with a water–gas shift reaction on a Rh single-atom catalyst without the use of ligands. Detailed studies revealed that the hydrogen generated in situ from the water–gas shift is critical for the highly regioselective formation of linear products. The coupling of a traditional homogeneous catalytic process with a heterogeneous catalytic reaction to tune product selectivity may provide a new avenue for the heterogenization of homogenous catalytic processes.
- Chen, Fang,Lang, Rui,Li, Tianbo,Qiao, Botao,Su, Yang,Wang, Aiqin,Wang, Hua,Zhang, Tao
-
supporting information
p. 7430 - 7434
(2020/03/13)
-
- Diethylsilane as a Powerful Reagent in Au Nanoparticle-Catalyzed Reductive Transformations
-
Diethylsilane (Et2SiH2), a simple and readily available dihydrosilane, that exhibits superior reactivity, as compared to monohydrosilanes, in a series of reductive transformations catalyzed by recyclable and reusable Au nanoparticles (1 mol-%) supported on TiO2. It reduces aldehydes or ketones almost instantaneously at ambient conditions. It can be used in a one pot rapid reductive amination procedure, in which premixing of aldehyde and amine is required prior to the addition of the reducing agent and the catalyst, even in a protic solvent. An unprecedented method for the synthesis of N-arylisoindolines is also shown in the reductive amination between o-phthalaldehyde and anilines. In this transformation, it is proposed that the intermediate N,2-diphenylisoindolin-1-imines are reduced stepwise to the isoindolines. Finally, Et2SiH2 readily reduces amides into amines in excellent yields and shorter reaction times relative to previously known analogous nano Au(0)-catalyzed protocols.
- Louka, Anastasia,Kidonakis, Marios,Saridakis, Iakovos,Zantioti-Chatzouda, Elisavet-Maria,Stratakis, Manolis
-
p. 3508 - 3514
(2020/06/02)
-
- C?H Amination via Nitrene Transfer Catalyzed by Mononuclear Non-Heme Iron-Dependent Enzymes
-
Expanding the reaction scope of natural metalloenzymes can provide new opportunities for biocatalysis. Mononuclear non-heme iron-dependent enzymes represent a large class of biological catalysts involved in the biosynthesis of natural products and catabolism of xenobiotics, among other processes. Here, we report that several members of this enzyme family, including Rieske dioxygenases as well as α-ketoglutarate-dependent dioxygenases and halogenases, are able to catalyze the intramolecular C?H amination of a sulfonyl azide substrate, thereby exhibiting a promiscuous nitrene transfer reactivity. One of these enzymes, naphthalene dioxygenase (NDO), was further engineered resulting in several active site variants that function as C?H aminases. Furthermore, this enzyme could be applied to execute this non-native transformation on a gram scale in a bioreactor, thus demonstrating its potential for synthetic applications. These studies highlight the functional versatility of non-heme iron-dependent enzymes and pave the way to their further investigation and development as promising biocatalysts for non-native metal-catalyzed transformations.
- Vila, Maria Agustina,Steck, Viktoria,Rodriguez Giordano, Sonia,Carrera, Ignacio,Fasan, Rudi
-
p. 1981 - 1987
(2020/04/17)
-
- Ir-catalyzed tandem hydroformylation-transfer hydrogenation of olefins with (trans-/cis-)formic acid as hydrogen source in presence of 1,10-phenanthroline
-
The one-pot tandem hydroformylation-reduction to synthesize alcohols from olefins is in great demand but suffering from low yields, poor selectivity and harsh condition. Herein, 1,10-phenanthroline (L1) modified Ir-catalyst proved to exhibit multiple cata
- Chen, Xiao-Chao,Gao, Han,Liu, Lei,Liu, Ye,Lu, Yong,Xia, Fei,Yang, Shu-Qing
-
p. 183 - 193
(2020/04/08)
-
- Manganese(I)-Catalyzed β-Methylation of Alcohols Using Methanol as C1 Source
-
Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO-iPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to “biohybrid” molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C?C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules.
- Kaithal, Akash,van Bonn, Pit,H?lscher, Markus,Leitner, Walter
-
supporting information
p. 215 - 220
(2019/12/03)
-
- Photo-triggered hydrogen atom transfer from an iridium hydride complex to unactivated olefins
-
Many photoactive metal complexes can act as electron donors or acceptors upon photoexcitation, but hydrogen atom transfer (HAT) reactivity is rare. We discovered that a typical representative of a widely used class of iridium hydride complexes acts as an H-atom donor to unactivated olefins upon irradiation at 470 nm in the presence of tertiary alkyl amines as sacrificial electron and proton sources. The catalytic hydrogenation of simple olefins served as a test ground to establish this new photo-reactivity of iridium hydrides. Substrates that are very difficult to activate by photoinduced electron transfer were readily hydrogenated, and structure-reactivity relationships established with 12 different olefins are in line with typical HAT reactivity, reflecting the relative stabilities of radical intermediates formed by HAT. Radical clock, H/D isotope labeling, and transient absorption experiments provide further mechanistic insight and corroborate the interpretation of the overall reactivity in terms of photo-triggered hydrogen atom transfer (photo-HAT). The catalytically active species is identified as an Ir(ii) hydride with an IrII-H bond dissociation free energy around 44 kcal mol-1, which is formed after reductive 3MLCT excited-state quenching of the corresponding Ir(iii) hydride, i.e. the actual HAT step occurs on the ground-state potential energy surface. The photo-HAT reactivity presented here represents a conceptually novel approach to photocatalysis with metal complexes, which is fundamentally different from the many prior studies relying on photoinduced electron transfer. This journal is
- Guo, Xingwei,Pfund, Bj?rn,Schreier, Mirjam R.,Wenger, Oliver S.
-
p. 8582 - 8594
(2020/09/07)
-
- Highly Enantioselective Catalytic Kinetic Resolution of α-Branched Aldehydes through Formal Cycloaddition with Homophthalic Anhydrides
-
A new catalytic methodology was developed to promote an efficient one-pot kinetic resolution of racemic aldehydes with selectivity (s*) of up to 91 (99:1 d.r., >99 % ee) in a cycloaddition reaction with enolizable anhydrides to afford dihydroisocoumarin products (a core prevalent in natural products and molecules of medicinal interest) containing three contiguous stereocentres.
- Farid, Umar,Aiello, Maria Luisa,Connon, Stephen J.
-
p. 10074 - 10079
(2019/07/18)
-
- Identification of an Esterase Isolated Using Metagenomic Technology which Displays an Unusual Substrate Scope and its Characterisation as an Enantioselective Biocatalyst
-
Evaluation of an esterase annotated as 26D isolated from a marine metagenomic library is described. Esterase 26D was found to have a unique substrate scope, including synthetic transformations which could not be readily effected in a synthetically useful manner using commercially available enzymes. Esterase 26D was more selective towards substrates which had larger, more sterically demanding substituents (i. e. iso-propyl or tert-butyl groups) on the β-carbon, which is in contrast to previously tested commercially available enzymes which displayed a preference for substrates with sterically less demanding substituents (e.g. methyl group) at the β-carbon. (Figure presented.).
- Gavin, Declan P.,Murphy, Edel J.,Foley, Aoife M.,Castilla, Ignacio Abreu,Reen, F. Jerry,Woods, David F.,Collins, Stuart G.,O'Gara, Fergal,Maguire, Anita R.
-
p. 2466 - 2474
(2019/03/11)
-
- Iridium-promoted conversion of terminal epoxides to primary alcohols under acidic conditions using hydrogen
-
A strategy for the conversion of terminal epoxides to primary alcohols is presented. The reaction uses hydrogen as the only stoichiometric reagent and is promoted by an iridium precatalyst under acidic conditions. Selectivity for the formation of a terminal alcohol over an internal alcohol is observed for both alkyl- and aryl-substituted terminal epoxides in isolated yields of up to 50% and 72% respectively.
- Rainsberry, Alena N.,Sage, Jarrod G.,Scheuermann, Margaret L.
-
p. 3020 - 3022
(2019/06/27)
-
- Polymer-Anchored Bifunctional Pincer Catalysts for Chemoselective Transfer Hydrogenation and Related Reactions
-
A series of polymer-supported cooperative PC(sp3)P pincer catalysts was synthesized and characterized. Their catalytic activity in the acceptorless dehydrogenative coupling of alcohols and the transfer hydrogenation of aldehydes with formic acid as a hydrogen source was investigated. This comparative study, examining homogeneous and polymer-tethered species, proved that carefully designing a link between the support and the catalytic moiety, which takes into consideration the mechanism underlying the target transformation, might lead to superior heterogeneous catalysis.
- Mujahed, Shrouq,Valentini, Federica,Cohen, Shirel,Vaccaro, Luigi,Gelman, Dmitri
-
p. 4693 - 4699
(2019/10/28)
-
- Polypyridyl iridium(III) based catalysts for highly chemoselective hydrogenation of aldehydes
-
Iridium-catalyzed transfer hydrogenation (TH) of carbonyl compounds using HCOOR (R = H, Na, NH4) as a hydrogen source is a pivotal process as it provides the clean process and is easy to execute. However, the existing highly efficient iridium catalysts work at a narrow pH; thus, does not apply to a wide variety of substrates. Therefore, the development of a new catalyst which works at a broad pH range is essential as it can gain a broader scope of utilization. Here we report highly efficient polypyridyl iridium(III) catalysts, [Ir(tpy)(L)Cl](PF6)2 {where tpy = 2,2′:6′,2′'-Terpyridine, L = phen (1,10-Phenanthroline), Me2phen (4,7-Dimethyl-1,10-phenanthroline), Me4phen (3,4,7,8-Tetramethyl-1,10-phenanthroline), Me2bpy (4,4′-Dimethyl-2–2′-dipyridyl)} for the chemoselective reduction of aldehydes to alcohols in aqueous ethanol and sodium formate as the hydride source. The reaction can be carried out efficiently in broad pH ranges, from pH 6 to 11. These catalysts are air stable, easy to prepare using commercially available starting materials, and are highly applicable for a wide range of substrates, such as electron-rich or deficient (hetero)arenes, halogens, phenols, alkoxy, ketones, esters, carboxylic acids, cyano, and nitro groups. Particularly, acid and hydroxy groups containing aldehydes were reduced successfully in basic and acidic reaction conditions, demonstrating the efficiency of the catalyst in a broad pH range with high conversion rates under microwave irradiation.
- Pandrala, Mallesh,Resendez, Angel,Malhotra, Sanjay V.
-
p. 283 - 288
(2019/09/30)
-
- Synthesis of β-Chiral Amines by Dynamic Kinetic Resolution of α-Branched Aldehydes Applying Imine Reductases
-
Imine reductases (IREDs) allow the one-step preparation of optically active secondary and tertiary amines by reductive amination of ketones. Until now, mainly α-chiral amines have been prepared by this route. In this study, we explored the possibility of synthesizing β-chiral amines, a class of compounds which is also frequently found as structural motif in pharmaceuticals but much more challenging to prepare due to the following reasons: (i) The aldehyde substrate already contains the chiral center and needs to be racemized to enable full conversion. (ii) Because the intermediate imine bears the stereo center two carbon atoms remote to the imine nitrogen, it is more challenging to achieve high enantioselectivity compared to α-chiral amine synthesis. For investigating the proof of concept, we first confirmed that different IREDs are able to convert a variety of α-branched aldehydes when combined with five different amine substrates. The IRED from Streptomyces ipomoeae was a suitable enzyme facilitating the dynamic kinetic resolution of 2-phenylpropanal and a substituted 2-methyl-3-phenylpropanal: the corresponding N-methylated β-chiral amines were obtained with '95 % conversion and 78 and 95 %ee. Other amines were formed with low to moderate enantiomeric excess. This exemplifies the potential of IREDs for the one-step synthesis of secondary β-chiral amines, but also the challenge to identify highly selective enzymes for a desired amine product.
- Matzel, Philipp,Wenske, Sebastian,Merdivan, Simon,Günther, Sebastian,H?hne, Matthias
-
p. 4281 - 4285
(2019/08/20)
-
- Mild Iridium-Catalysed Isomerization of Epoxides. Computational Insights and Application to the Synthesis of β-Alkyl Amines
-
The isomerization of epoxides to aldehydes using the readily available Crabtree's reagent is described. The aldehydes were transformed into synthetically useful amines by a one-pot reductive amination using pyrrolidine as imine-formation catalyst. The reactions worked with low catalyst loadings in very mild conditions. The procedure is operationally simple and tolerates a wide range of functional groups. A DFT study of its mechanism is presented showing that the isomerization takes place via an iridium hydride mechanism with a low energy barrier, in agreement with the mild reaction conditions. (Figure presented.).
- Cabré, Albert,Cabezas-Giménez, Juanjo,Sciortino, Giuseppe,Ujaque, Gregori,Verdaguer, Xavier,Lledós, Agustí,Riera, Antoni
-
supporting information
p. 3624 - 3631
(2019/07/10)
-
- Ruthenium-Catalyzed Selective Hydrogenation of Epoxides to Secondary Alcohols
-
A ruthenium(II)-catalyzed highly selective Markovnikov hydrogenation of terminal epoxides to secondary alcohols is reported. Diverse substitutions on the aryl ring of styrene oxides are tolerated. Benzylic, glycidyl, and aliphatic epoxides as well as diepoxides also underwent facile hydrogenation to provide secondary alcohols with exclusive selectivity. Metal-ligand cooperation-mediated ruthenium trans-dihydride formation and its reaction involving oxygen and the less substituted terminal carbon of the epoxide is envisaged for the origin of the observed selectivity.
- Thiyagarajan, Subramanian,Gunanathan, Chidambaram
-
supporting information
p. 9774 - 9778
(2019/12/02)
-
- Iron-Catalyzed Borrowing Hydrogen β- C(sp3)-Methylation of Alcohols
-
Herein we report the iron-catalyzed β-C(sp3)-methylation of primary alcohols using methanol as a C1 building block. This borrowing hydrogen approach employs a well-defined bench-stable (cyclopentadienone)iron(0) carbonyl complex as precatalyst (5 mol %) and enables a diverse selection of substituted 2-arylethanols to undergo β-C(sp3)-methylation in good isolated yields (24 examples, 65% average yield).
- Polidano, Kurt,Williams, Jonathan M. J.,Morrill, Louis C.
-
p. 8575 - 8580
(2019/09/12)
-
- Diaminodiphosphine tetradentate ligand and ruthenium complex thereof, and preparation methods and applications of ligand and complex
-
The invention discloses a diaminodiphosphine tetradentate ligand and a ruthenium complex thereof, and preparation methods and applications of the ligand and the complex, and provides a ruthenium complex represented by a formula I, wherein L is a diaminodiphosphine tetradentate ligand represented by a formula II, and X and Y are respectively and independently chlorine ion, bromine ion, iodine ion,hydrogen negative ion or BH4. According to the present invention, the ruthenium complex exhibits excellent catalytic activity in the catalytic hydrogenation reactions of ester compounds, has high yield and high chemical selectivity, is compatible with conjugated and non-conjugated carbon-carbon double bond, carbon-carbon triple bond, epoxy, halogen, carbonyl and other functional groups, and hasgreat application prospects.
- -
-
Paragraph 0301-0303; 0306
(2019/11/04)
-
- Iron-Catalyzed β-Alkylation of Alcohols
-
β-Branched alkylated alcohols have been prepared in good yields using a double-hydrogen autotransfer strategy in the presence of our diaminocyclopentadienone iron tricarbonyl complex Fe1. The alkylation of some 2-arylethanol derivatives was successfully addressed with benzylic alcohols and methanol as alkylating reagents under mild conditions. Deuterium labeling experiments suggested that both alcohols (2-arylethanol and either methanol or benzyl alcohol) served as hydrogen donors in this cascade process.
- Bettoni, Leó,Gaillard, Sylvain,Renaud, Jean-Luc
-
supporting information
p. 8404 - 8408
(2019/10/16)
-
- Ruthenium(II)-Catalyzed β-Methylation of Alcohols using Methanol as C1 Source
-
Selective introduction of methyl branches into the carbon chains of alcohols can be achieved with low loadings of ruthenium precatalyst [RuH(CO)(BH4)(HN(C2H4PPh2)2)] (Ru-MACHO-BH) using methanol both as methylating reagent and as reaction medium. A wide range of structurally divers alcohols was β-methylated with excellent selectivity (>99 %) in fair to high yields (up to 94 %) under standard conditions, and turnover numbers up to 18,000 could be established. The overall reaction rate of the complex catalytic network appears to be governed by interconnection of the individual subcycles through availability of the reactive intermediates. The synthetic procedure opens pathways to important structural motifs following the Green Chemistry principles.
- Kaithal, Akash,Schmitz, Marc,H?lscher, Markus,Leitner, Walter
-
p. 5287 - 5291
(2019/05/28)
-
- Nanoporous Na+-montmorillonite perchloric acid as an efficient and recyclable catalyst for the chemoselective protection of hydroxyl groups
-
Nanoporous Na+-montmorillonite perchloric acid as a novel heterogeneous reusable solid acid catalyst was easily prepared by treatment of Na+-montmorillonite as a cheap and commercially available support with perchloric acid. The catalyst was characterized using a variety of techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), energy dispersive X-ray spectroscopy (EDX), pH analysis and determination of the Hammett acidity function. The prepared reagent showed excellent catalytic activity for the chemoselective conversion of alcohols and phenols to their corresponding trimethylsilyl ethers with 1,1,1,3,3,3-hexamethyldisilazane (HMDS) at room temperature. Deprotection of the resulting trimethylsilyl ethers can also be carried out using the same catalyst in ethanol. All reactions were performed under mild and completely heterogeneous reaction conditions in good to excellent yields. The notable advantages of this protocol are: short reaction times, high yields, availability and low cost of the reagent, easy work-up procedure and the reusability of the catalyst during a simple filtration.
- Mashhadinezhad, Maryam,Shirini, Farhad,Mamaghani, Manouchehr
-
p. 2099 - 2107
(2019/01/03)
-
- Selective ligand-free cobalt-catalysed reduction of esters to aldehydes or alcohols
-
Cobalt(ii) salts combined with NaBHEt3 and eventually a base catalyse efficiently and selectively the reduction of esters to aldehydes or alcohols through hydrosilylation by using phenylsilane. Catalyst characterisation by XRD, XPS, TEM and STEM analyses indicates the materials were partially crystalline with the presence of cobalt nanoparticles. Control experiments suggested low valent Co(0) was the active catalytic species involved.
- Rysak, Vincent,Descamps-Mandine, Armel,Simon, Pardis,Blanchard, Florent,Burylo, Laurence,Trentesaux, Martine,Vandewalle, Maxence,Collière, Vincent,Agbossou-Niedercorn, Francine,Michon, Christophe
-
p. 3504 - 3512
(2018/07/29)
-
- Manganese Catalyzed Hydrogenation of Enantiomerically Pure Esters
-
A manganese-catalyzed hydrogenation of esters has been accomplished with TONs up to 1000, using cheap, environmentally benign, potassium carbonate and simple alcohols as activator and solvent, respectively. The weakly basic conditions lead to good functional group tolerance and enable the hydrogenation of enantiomerically enriched α-chiral esters with essentially no loss of stereochemical integrity.
- Widegren, Magnus B.,Clarke, Matthew L.
-
supporting information
p. 2654 - 2658
(2018/05/17)
-
- C -Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
-
A versatile, selective, and recyclable heterogeneous catalytic method for the methylation of C-H bonds in alcohols, ketones, and indoles with methanol under oxidant-free conditions using a Pt-loaded carbon (Pt/C) catalyst in the presence of NaOH is reported. This catalytic system is effective for various methylation reactions: (1) the β-methylation of primary alcohols, including aryl, aliphatic, and heterocyclic alcohols, (2) the α-methylation of ketones, and (3) the selective C3-methylation of indoles. The reactions are driven by a borrowing-hydrogen mechanism. The reaction begins with the dehydrogenation of the alcohol(s) to afford aldehydes, which subsequently undergo a condensation reaction with the nucleophile (aldehyde, ketone, or indole), followed by hydrogenation of the condensation product by Pt-H species to yield the desired product. In all of the methylation reactions explored in this study, the Pt/C catalyst exhibits a significantly higher turnover number than other previously reported homogeneous catalytic systems. Moreover, it is demonstrated that the high catalytic activity of Pt can be rationalized in terms of the adsorption energy of hydrogen on the metal surface, as revealed by density functional theory calculations on different metal surfaces.
- Siddiki, S. M. A. Hakim,Touchy, Abeda S.,Jamil, Md. A. R.,Toyao, Takashi,Shimizu, Ken-Ichi
-
p. 3091 - 3103
(2018/04/14)
-
- A KIT FOR DETERMINING THE ABSOLUTE CONFIGURATION OF ALCOHOLS USING A COMPETING ENANTIOSELECTIVE CONVERSION APPROACH
-
Provided herein is a kit for the determination of the absolute configuration of alcohols of a competing enantioselective conversion approach.
- -
-
Paragraph 0036; 0055
(2018/06/06)
-
- Biocatalytic Parallel Interconnected Dynamic Asymmetric Disproportionation of α-Substituted Aldehydes: Atom-Efficient Access to Enantiopure (S)-Profens and Profenols
-
The biocatalytic asymmetric disproportionation of aldehydes catalyzed by horse liver alcohol dehydrogenase (HLADH) was assessed in detail on a series of racemic 2-arylpropanals. Statistical optimization by means of design of experiments (DoE) allowed the identification of critical interdependencies between several reaction parameters and revealed a specific experimental window for reaching an ′optimal compromise′ in the reaction outcome. The biocatalytic system could be applied to a variety of 2-arylpropanals and granted access in a redox-neutral manner to enantioenriched (S)-profens and profenols following a parallel interconnected dynamic asymmetric transformation (PIDAT). The reaction can be performed in aqueous buffer at ambient conditions, does not rely on a sacrificial co-substrate, and requires only catalytic amounts of cofactor and a single enzyme. The high atom-efficiency was exemplified by the conversion of 75 mM of rac-2-phenylpropanal with 0.03 mol% of HLADH in the presence of ~0.013 eq. of oxidized nicotinamide adenine dinucleotide (NAD+), yielding 28.1 mM of (S)-2-phenylpropanol in 96% ee and 26.5 mM of (S)-2-phenylpropionic acid in 89% ee, in 73% overall conversion. Isolated yield of 62% was obtained on 100 mg-scale, with intact enantiopurities. (Figure presented.).
- Tassano, Erika,Faber, Kurt,Hall, Mélanie
-
supporting information
p. 2742 - 2751
(2018/07/29)
-
- Deaminative Borylation of Aliphatic Amines Enabled by Visible Light Excitation of an Electron Donor–Acceptor Complex
-
A deaminative strategy for the borylation of aliphatic primary amines is described. Alkyl radicals derived from the single-electron reduction of redox-active pyridinium salts, which can be isolated or generated in situ, were borylated in a visible light-mediated reaction with bis(catecholato)diboron. No catalyst or further additives were required. The key electron donor–acceptor complex was characterized in detail by both experimental and computational investigations. The synthetic potential of this mild protocol was demonstrated through the late-stage functionalization of natural products and drug molecules.
- Sandfort, Frederik,Strieth-Kalthoff, Felix,Klauck, Felix J. R.,James, Michael J.,Glorius, Frank
-
supporting information
p. 17210 - 17214
(2018/11/10)
-
- Impact of variation of the acyl group on the efficiency and selectivity of the lipase-mediated resolution of 2-phenylalkanols
-
By tuning the steric properties of the acyl group to control the efficiency and selectivity of the resolution, 2-phenyl-1-propanol 1a was prepared by lipase-catalysed hydrolysis using a short-chain acyl group, with E-values of up to 66 (ee up to 95%). 2-Phenylbutan-1-ol 1b was similarly resolved (up to 86% ee) using the optimised conditions, while the ester of the more sterically demanding 3-methyl-2-phenylbutan-1-ol 1c proved resistant to enzymatic hydrolysis under these conditions.
- Foley, Aoife M.,Gavin, Declan P.,Joniec, Ilona,Maguire, Anita R.
-
supporting information
p. 1144 - 1153
(2017/09/15)
-
- Biocatalytic Formal Anti-Markovnikov Hydroamination and Hydration of Aryl Alkenes
-
Biocatalytic anti-Markovnikov alkene hydroamination and hydration were achieved based on two concepts involving enzyme cascades: epoxidation-isomerization-amination for hydroamination and epoxidation-isomerization-reduction for hydration. An Escherichia coli strain coexpressing styrene monooxygenase (SMO), styrene oxide isomerase (SOI), ω-transaminase (CvTA), and alanine dehydrogenase (AlaDH) catalyzed the hydroamination of 12 aryl alkenes to give the corresponding valuable terminal amines in high conversion (many ≥86%) and exclusive anti-Markovnikov selectivity (>99:1). Another E. coli strain coexpressing SMO, SOI, and phenylacetaldehyde reductase (PAR) catalyzed the hydration of 12 aryl alkenes to the corresponding useful terminal alcohols in high conversion (many ≥80%) and very high anti-Markovnikov selectivity (>99:1). Importantly, SOI was discovered for stereoselective isomerization of a chiral epoxide to a chiral aldehyde, providing some insights on enzymatic epoxide rearrangement. Harnessing this stereoselective rearrangement, highly enantioselective anti-Markovnikov hydroamination and hydration were demonstrated to convert α-methylstyrene to the corresponding (S)-amine and (S)-alcohol in 84-81% conversion with 97-92% ee, respectively. The biocatalytic anti-Markovnikov hydroamination and hydration of alkenes, utilizing cheap and nontoxic chemicals (O2, NH3, and glucose) and cells, provide an environmentally friendly, highly selective, and high-yielding synthesis of terminal amines and alcohols.
- Wu, Shuke,Liu, Ji,Li, Zhi
-
p. 5225 - 5233
(2017/08/17)
-
- Rhodium-Catalyzed Asymmetric Synthesis of β-Branched Amides
-
A general asymmetric route for the one-step synthesis of chiral β-branched amides is reported through the highly enantioselective isomerization of allylamines, followed by enamine exchange, and subsequent oxidation. The enamine exchange allows for a rapid and modular synthesis of various amides, including challenging β-diaryl and β-cyclic.
- Wu, Zhao,Laffoon, Joshua D.,Nguyen, Trang T.,McAlpin, Jacob D.,Hull, Kami L.
-
supporting information
p. 1371 - 1375
(2017/01/24)
-