Reduction Of Carbonyl Compounds Research Articles

Enzymatic synthesis of enantiopure alcohols: current state and perspectives.

Enantiomerically pure alcohols, as key intermediates, play an essential role in the pharmaceutical, agrochemical and chemical industries. Among the methods used for their production, biotechnological approaches are generally considered a green and effective alternative due to their mild reaction conditions and remarkable enantioselectivity. An increasing number of enzymatic strategies for the synthesis of these compounds has been developed over the years, among which seven primary methodologies can be distinguished as follows: (1) enantioselective water addition to alkenes, (2) enantioselective aldol addition, (3) enantioselective coupling of ketones with hydrogen cyanide, (4) asymmetric reduction of carbonyl compounds, (5) (dynamic) kinetic resolution of racemates, (6) enantioselective hydrolysis of epoxides, and (7) stereoselective hydroxylation of unactivated C–H bonds. Some recent reviews have examined these approaches separately; however, to date, no review has included all the above mentioned strategies. The aim of this mini-review is to provide an overview of all seven enzymatic strategies and draw conclusions on the effect of each approach.

B(C6F5)3-Catalyzed Chemoselective Reduction of Carbonyl Compounds under Water Conditions

B(C₆F₅)₃-Catalyzed Chemoselective Reduction of Carbonyl Compounds under Water Conditions

Electrocatalytic Hydrogenation of Oxygenated Compounds in Aqueous Phase

Electrocatalytic hydrogenation is a strategy to hydrogenate biogenic compounds under ambient conditions by replacing the thermal and H2 inputs by cathodic potential. This work compares the performances of this approach (in aqueous phase at room temperature) for the conversion of a variety of model oxygenated compounds over a series of metals. The target functionalities were carbonyl groups, aromatic rings, and ether bonds. All of the metals explored (Pt, Rh, Pd, and Cu) are active for the reduction of carbonyl compounds to alcohols. The conversion rate of benzaldehyde increased as a function of the metal as Pt < Rh < Pd (Cu was tested under different conditions). In contrast, only Rh and Pt were active for hydrogenation of aromatic rings (Rh was more active than Pt). In a comparison of the target functionalities, carbonyl groups are more reactive than aromatic rings and ether bonds in phenolic compounds and diaryl ethers on all of the explored metals. This carbonyl reactivity, however, is enhanced by the ...

Polydopamine: An Emerging Material in the Catalysis of Organic Transformations

Polydopamine, a ‘mussel-inspired’ polymer, has been explored extensively in materials science as a universal coating. However, as an easily available, stable and environmentally benign material, it has recently been discovered to demonstrate catalytic applications. In this short review, we briefly discuss the main approaches employing polydopamine in the catalysis of organic transformations. These include metal/polydopamine-type systems and metal-free approaches that exploit the acid/base properties of this versatile polymer.1 Introduction2 PDA and Metal Catalysis2.1 Reduction of Nitroaryl Compounds to Anilines2.2 Reduction of Carbonyl Compounds to Alcohols2.3 Suzuki and Heck Coupling Reactions2.4 Other Reactions Catalyzed by M/PDA-Type Systems3 PDA as a Catalyst Itself4 Conclusion

Highly Selective Transfer Hydrogenation of Carbonyl Compounds Using La2O3

Abstract In the present study, we used rare earth oxides for the catalytic transfer hydrogenation of carbonyl compounds. Pre-treated La2O3 showed better catalytic performance than various rare earth oxides for the reduction of carbonyl compounds. Reaction conditions, precursors, and donor hydrogen sources were also investigated to optimize the hydrogen transfer to furfural in 2-propanol. La2O3 provided a conversion of different carbonyl compounds and selectivity to the corresponding alcohols up to 100% and 99%, respectively. We also investigated a plausible mechanism using in situ IR and found that furfural was adsorbed on the catalyst surface in a different adsorption mode. Meanwhile, La(OH)3, a hydroxide derivative of La2O3 formed during the reaction, was also catalytically active.

Selective Reduction of Ketones and Aldehydes in Continuous-Flow Microreactor—Kinetic Studies

In this work, the kinetics of Meerwein–Ponndorf–Verley chemoselective reduction of carbonyl compounds was studied in monolithic continuous-flow microreactors. To the best of our knowledge, this is the first report on the MPV reaction kinetics performed in a flow process. The microreactors are a very attractive alternative to the batch reactors conventionally used in this process. The proposed micro-flow system for synthesis of unsaturated secondary alcohols proved to be very efficient and easily controlled. The microreactors had reactive cores made of zirconium-functionalized silica monoliths of excellent catalytic properties and flow characteristics. The catalytic experiments were carried out with the use of 2-butanol as a hydrogen donor. Herein, we present the kinetic parameters of cyclohexanone reduction in a flow reactor and data on the reaction rate for several important ketones and aldehydes. The lack of diffusion constraints in the microreactors was demonstrated. Our results were compared with those from other authors and demonstrate the great potential of microreactor applications in fine chemical and complex intermediate manufacturing.

Meervein-Ponndorf-Vereley reduction of carbonyl compounds in monolithic siliceous microreactors doped with Lewis acid centres

Meerwein-Ponndorf-Vereley chemoselective reduction of cyclohexanone and benzaldehyde was studied in monolithic continuous-flow microreactors, with various Lewis acid centres derived from different metal precursors, i.e. metal alkoxides, chelated metal alkoxides and salts. The productivities achieved in the microreactors, doped with metal centres terminated by propoxy ligands, were significantly higher, ca. 30%, than those obtained for oxides modified monoliths. The highest efficiency of Zr-doped microreactors was proved and their superiority over aluminium and titanium functionalized ones was demonstrated. Higher efficiency of microreactors compared to batch reactors with powdered catalysts has been shown. Stability of proposed materials has been demonstrated. The catalytic outcomes were correlated with structural and physicochemical properties of materials, obtained using low-temperature nitrogen adsorption, mercury porosimetry, SEM microscopy, ICP-MS, FTIR study and pyridine adsorption.

Conjugate Reductions of Carbonyl Compounds with Diazaphospholenes

Key words asymmetric catalysis - reduction - enamides - diazaphospholenes - enones

Biomass-derived mesoporous Hf-containing hybrid for efficient Meerwein-Ponndorf-Verley reduction at low temperatures

The use of organic chemicals derived from renewable sources to synthesize functional solid materials for heterogeneous catalysis is of great significance. Herein, a new porous and acid-base bifunctional hybrid (FDCA-Hf) was designed and prepared by simple assembly of biomass-derived 2,5-furandicarboxylic acid (FDCA) with hafnium (Hf) under template-free conditions. The resulting FDCA-Hf hybrid with mesopores centered at 6.9 nm, moderate surface area (365.8 m2/g) and acid-base couple sites (density: 0.51 vs 0.97 mmol/g, acid/base molar ratio: 0.53), could selectively catalyze the Meerwein-Ponndorf-Verley reduction of carbonyl compounds under mild reaction conditions (as low as 90 °C in a short time of 1 h), especially of ethyl levulinate to γ-valerolactone, in quantitative yields (95–100%) and relatively higher reaction rate (e.g., turnover frequency: 2.28 h−1) compared to other catalysts. Moreover, the efficient simultaneous (trans)esterification of Jatropha oils with high acidic values to biodiesel (up to 98% yield) could also be achieved over FDCA-Hf with robust acid-base catalytic sites. The FDCA-Hf hybrid was highly stable due to the presence of robust metal-organic framework and could be resued with no decline in activity. Further studies demonstrated that the synergistic role of Lewis acid-base couple species (Hf4+–O2−) and Brønsted acidic species (OH) of FDCA-Hf contributed greatly to its pronounced catalytic activity.

Biotechnological Properties of Sponges from Northeast Brazil: Cliona varians as a Biocatalyst for Enantioselective Reduction of Carbonyl Compounds

To research the potential ability of whole marine sponges to act as biocatalysts, this paper describes for the first time the employment of whole Cliona varians sponge in the stereoselective reduction of prochiral a-keto esters and isatin to the corresponding chiral alcohols. The addition of D-fructose, D-glucose or sucrose remarkably increased the conversion ratios and stereoselectivities by this marine sponge. Furthermore, in the presence of D-glucose and D-maltose, the reduction of isatin by C. varians afforded the corresponding 3-hydroxyindolin-2-one with high conversions (85-90%) and good enantioselectivities (60-74%). These results showed that the marine sponge presents great potential to be used as biocatalyst for stereoselective reduction of carbonyl compounds.

Synthesis of silyl iron hydride via Si-H activation and its dual catalytic application in the hydrosilylation of carbonyl compounds and dehydration of benzamides.

The hydrido silyl iron complex (o-Ph2PC6H4SiMe2)Fe(PMe3)3H (2) was obtained via the activation of the Si-H bond of the bidentate silyl ligand o-Ph2P(C6H4)SiMe2H (1) by Fe(PMe3)4. 2 showed good to excellent catalytic activity in both the reduction of aldehydes/ketones and the dehydration of benzamide. In addition, with complex 2 as a catalyst, α,β-unsaturated carbonyls could be selectively reduced to the corresponding α,β-unsaturated alcohols. The mechanisms of the formation of 2 and the catalytic dehydration process are proposed and partly experimentally verified.

Remarkably high catalyst efficiency of a disilaruthenacyclic complex for hydrosilane reduction of carbonyl compounds.

A disilaruthenacyclic complex (1) showed extremely high catalytic activity for hydrosilane reduction of aldehydes and ketones to silyl ethers and secondary and tertiary amides to the corresponding amines. An σ-CAM mechanism was proposed to explain the activity.

Construction of PQQ-Enzyme Multi-Immobilized Electrodes for Electrocatalytic Reduction of Carbonyl Compounds

Construction of PQQ-Enzyme Multi-Immobilized Electrodes for Electrocatalytic Reduction of Carbonyl Compounds

A Manganese Pre-Catalyst: Mild Reduction of Amides, Ketones, Aldehydes, and Esters.

A new (N-phosphinoamidinate)manganese complex is shown to be a useful pre-catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn-catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition-metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.

A Manganese Pre‐Catalyst: Mild Reduction of Amides, Ketones, Aldehydes, and Esters

AbstractA new (N‐phosphinoamidinate)manganese complex is shown to be a useful pre‐catalyst for the hydrosilative reduction of carbonyl compounds, and in most cases at room temperature. The Mn‐catalyzed reduction of tertiary amides to tertiary amines, with a useful scope, is demonstrated for the first time by use of this catalyst, and is competitive with the most effective transition‐metal catalysts known for such transformations. Ketones, aldehydes, and esters were also successfully reduced under mild conditions by using this new Mn catalyst.

Enantioselective Reductions Promoted by (Cyclopentadienone)iron Complexes.

(Cyclopentadienone)iron complexes have recently gained widespread interest as cheap metal-based pre-catalysts for the reduction of carbonyl compounds and imines, thanks to their air- and moisture-stability and easy synthesis/purification. In this account, several approaches are presented to achieve enantioselective C=O and C=N bond reduction using this class of iron complexes. Most of the examples, used in the asymmetric reduction of ketones, rely on chiral (cyclopentadienone)iron complexes, featuring a chiral cyclopentadienone backbone and/or a chiral monophosphoramidite ligand, introduced by replacement of a CO ligand. The enantiomeric excesses achieved so far with this strategy are at best moderate. Better ees could be obtained with an alternative approach, used in the enantioselective reduction of C=N bonds, which consists in combining an achiral (hydroxycyclopentadienyl)iron complex (i.e. the activated form of a (cyclopentadienone)iron complex) with a chiral phosphoric acid.

Zinc‐Mediated Efficient and Selective Reduction of Carbonyl Compounds

We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double‐bond functional groups. A broad functional‐group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.

Palladium on Polydopamine: Its True Potential in Catalytic Transfer Hydrogenations and Heck Coupling Reactions

AbstractThe application of Pd–polydopamine and magnetic Fe3O4@Pd–polydopamine catalysts in catalytic transfer hydrogenation reactions and the Heck arylation is reported. The reduction of a wide range of aromatic nitro‐compounds bearing both electron‐donating and ‐withdrawing substituents to the corresponding anilines could be efficiently performed, although the reduction of carbonyl compounds was found to be less general. In the latter case, only aromatic ketones could be reduced to the corresponding alcohols, whereas aldehyde substrates were unaffected, which may be owing to their reaction with the catalyst support leading to catalyst deactivation. By using magnetic Fe3O4@Pd–polydopamine system, facilitated catalyst recovery and reuse for five consecutive cycles without considerable loss of activity in nitro‐group reduction. The efficiency of the catalyst in Heck reactions was comparable to that in transfer hydrogenation, however, no catalytic activity was observed upon reuse in this case, likely as a result of metal leaching. We also explored tandem Heck reaction/catalytic transfer hydrogenation sequences, however, the two reactions showed limited compatibility under the applied conditions.

Selection of microbial biocatalysts for the reduction of cyclic and heterocyclic ketones

The reduction of carbonyl compounds plays an important role in the synthesis of complex chiral molecules. In particular, enantiopure substituted cyclic and heterocyclic compounds are useful intermediates for the synthesis of several antiviral, antitumor, and antibiotic agents, and recently, they have also been used as organocatalysts for C-C addition. Alcohol dehydrogenases (ADH) are enzymes involved in the transformation of prochiral ketones to chiral hydroxyl compounds. While significant scientific effort has been paid to the use of aliphatic and exocyclic ketones as ADH substrates, reports on (hetero)cyclic carbonyl compounds as substrates of these enzymes are scarce. In the present study, 109 bacteria and 36 fungi were screened, resulting in 10 organisms belonging to both kingdoms capable of transforming cyclic and heterocyclic ketones into the corresponding alcohols. Among them, Erwinia chrysanthemi could quantitatively reduce cyclododecanone and Geotrichum candidum could stereoselectively reduce N-Boc-3-piperidone and N-Boc-3-pyrrolidinone to their corresponding (S)-alcohols; however, the anti-Prelog isomer was obtained when acetophenone was the substrate.

Catalyst Design of Iron Complexes

Abstract Despite worldwide interest from synthetic chemists, the rational design of catalytically active organoiron species remains problematic. While noble metal catalysis proceeds through diamagnetic low-spin intermediates, iron species are often in the high or intermediate spin states, which are paramagnetic and difficult to analyze. Possible spin change during catalysis also complicates the problem. This report describes two extremes for the catalyst design of iron complexes. One involves diamagnetic 14-electron iron(II) species useful for two-electron chemistry often seen in noble metal catalysis. The disilaferracyclic carbonyl complex 4 is a good catalyst precursor, and shows good catalytic performance for the hydrogenation and hydrosilylation of alkenes, and the hydrosilane reduction of carbonyl compounds. Based on DFT calculations, mechanisms involving σ-CAM (sigma-complex-assisted metathesis) for the hydrogenation and hydrosilane reduction are suggested. Further catalyst design inspired by the success of 4 led to the discovery of iron and cobalt catalyst systems composed of metal carboxylates and isocyanide ligands leading to a practical substitute for industrially useful platinum catalysts for hydrosilylation with hydrosiloxanes. The second approach involves paramagnetic 16-electron iron (II) catalyst species. A series of “(R3TACN)FeX2” complexes were prepared and found to be good catalysts for atom transfer radical polymerization, giving rise to well-controlled polymerization of styrene, methacrylates, and acrylates with high activity. Moreover, the catalyst could be easily removed from the polymer and was reusable. Mechanistic studies of iron-catalyzed cross-coupling reactions in collaboration with Nakamura and Takaya opened a new approach to the catalyst design of unknown spin states by using new analytical methods for paramagnetic species in the solution state.