Ligand-Assisted Rate Acceleration in Lanthanum(III) Isopropoxide Catalyzed Transesterification of Carboxylic Esters

Computational and experimental identification of an exceptionally efficient ethyl ester synthetase with broad substrate specificity and high product yield, suggests potential for industrial biocatalysis

Transesterification plays a crucial role in the synthesis of diverse esters in organic synthesis but is barely reported in biocatalysis. Here, we computationally identify the salicylic acid-binding protease 2 (SABP2) as an efficient ethyl ester bond synthetase by QM/MM MD and free energy simulations and present the practical and effective utilization of SABP2 as an eco-friendly biocatalyst for transesterification reactions by a series of experiments. Our findings demonstrate that SABP2 efficiently catalyzes the transesterification reaction between the carboxyl acid group of promiscuous aromatic substrates and ethanol to produce the corresponding ethyl esters. Notably, while SABP2 exhibits its native capability to catalyze the hydrolysis of the methyl salicylate (MeSA), the transesterification rate (producing ethyl salicylate, EtSA) is about 3500 times higher than the hydrolysis rate. Additionally, a range of aromatic methyl esters are employed in the transesterification process, resulting in high yields (up to 98.9 %) of the corresponding ethyl esters. These results indicate a broad substrate scope for SABP2-catalyzed transesterification reactions, demonstrating its potential as a valuable biocatalyst for ester synthesis in industry.

Photocatalyzed Oxidative Tandem Reaction Mediated by Bipyridinium for Multifunctional Derivatization of Alcohols

The multifunctional derivatization of alcohols has been achieved by the bipyridinium-based conjugated small molecule photocatalysts with redox center and Lewis acid site. Besides exhibiting high activity in the selective generation of aldehydes/ketones, acids from alcohols through solvent modulation, this system renders the first selective synthesis of esters via an attractive cross-coupling pattern, whose reaction route is significantly different from the traditional condensation of alcohols and acids or esterification from hemiacetals. Following the oxidization of alcohol to aldehyde via bipyridinium-mediated electron and energy transfer, the Lewis acid site of bipyridinium then activates the aldehyde and methanol to obtain the acetal, which further reacts with methanol to generate ester. This method not only demonstrates a clear advantage of bipyridinium in diverse catalytic activities, but also paves the way for designing efficient multifunctional small molecule photocatalysts. This metal- and additive-free photocatalytic esterification reaction marks a significant advancement towards a more environmentally friendly, cost-effective and green sustainable approach, attributed to the utilization of renewable substrate alcohol and the abundant, low-cost air as the oxidant. The mildness of this esterification reaction condition provides a more suitable alternative for large-scale industrial production of esters.

Cellulose carbamates via transcarbamoylation/transurethanization of methyl carbamates in superbase-acid conjugate ionic liquids

A sustainable homogeneous transcarbamoylation/transurethanization protocol for cellulose modification with methyl N-substituted carbamates was developed. The protocol utilizes the superbase ionic liquid [mTBNH][OAc], not only as a green reaction medium, but also as a promotor of the transformation. This approach allows to obtain different cellulose carbamates with controllable degrees of substitution. The solubility of the obtained materials from the newly developed method was compared with the solubility of materials obtained from the isocyanate approach, where some intrinsic trends were observed.

Bulky magnesium(ii) and sodium(i) bisphenoxide catalysts for chemoselective transesterification of methyl (meth)acrylates

Given the industrial importance of (meth)acrylate esters, various groups have devoted considerable effort to investigating their chemoselective transesterification. In 2021, we developed magnesium(ii) and sodium(i) complexes derived from 2,6-di-tert-butyl-p-cresol (BHT-H) as chemoselective catalysts for the transesterification of methyl acrylate (MA) and methyl methacrylate (MMA), respectively. Based on our results, we report the discovery of magnesium(ii) and sodium(i) salts derived from 6,6'-(propane-2,2'-diyl)bis(2,4-di-tert-butylphenol) (PBTP-H₂), i.e. Mg(PBTP) and Na₂(PBTP), which are 41 and 81 times more effective catalysts than Mg(BHT)₂ and Na(BHT) for the transesterification of MA and MMA, respectively. These new catalysts are highly effective across an extensive range of alcohols, including primary and secondary alcohols, diols, and triols. Overall, this efficient transesterification technology can be expected to find practical applications in industrial process chemistry.

La(III)-Catalysed degradation of polyesters to monomers via transesterifications

Tris(acetylacetonato)lanthanum(III) (1 mol%) catalyses the degradation of poly(butylene succinate) (Mw = 90,700) by transesterification in MeOH at 90 ˚C for 4 h, thus affording dimethyl succinate (>99% yield) and 1,4-butanediol...

Practical Chemoselective Acylation: Organocatalytic Chemodivergent Esterification and Amidation of Amino Alcohols with N-Carbonylimidazoles

Chemoselective transformations are a cornerstone of efficient organic synthesis; however, achieving this goal for even simple transformations like acylations is often a challenge. We report that N -carbonylimidazoles undergo catalytic chemodivergent acylations of anilines or alcohols in the presence of pyridinium ions or DBU (1,8-Diazabicyclo[5.4.0]undec-7-ene), respectively. Both of these acylations display simultaneously high and broad chemoselectivity for the target group. Unprecedented levels of chemoselectivity were achieved in the DBU-catalyzed esterification: a single esterification product was obtained from a molecule containing primary aniline, alcohol, phenol, secondary amide, and N- H indole groups. These acylations are highly practical as they involve only readily available, inexpensive, and relatively safe reagents; can be performed at the multigram scale; and can be used on carboxylic acids directly via in situ formation of the acylimidazole electrophile. Reaction discovery, scope, assessment of practicality, and preliminary mechanistic investigations are discussed.

Development of Catalytic Reactions for Precise Control of Chemoselectivity

Catalytic chemoselective reactions of innately less reactive functionalities over more reactive functionalities are described. A cooperative catalyst comprising a soft Lewis acid/hard Brønsted base enabled chemoselective activation of a hydroxyl group over an amino group, allowing for nucleophilic addition to electron-deficient olefins. The reaction could be applicable for a variety of amino alcohols, including pharmaceuticals, without requiring a tedious protection-deprotection process. Chemoselective enolization and subsequent α-functionalization of carboxylic acid derivatives were also achieved by a redox active catalyst through the radical process, providing unnatural α-amino/hydroxy acid derivatives bearing a complex carbon framework and a diverse set of functionalities. The present chemoselective catalysis described herein offers new opportunities to expand the chemical space for innovative drug discovery research.

Insight into the Mechanism of the Acylation of Alcohols with Acid Anhydrides Catalyzed by Phosphoric Acid Derivatives

Insight into the mechanism of a safe, simple, and inexpensive phosphoric acid (H₃PO₄)-catalyzed acylation of alcohols with acid anhydrides is described. The corresponding in situ-generated diacylated mixed anhydrides, unlike traditionally proposed monoacylated mixed anhydrides, are proposed as the active species. In particular, the diacylated mixed anhydrides act as efficient catalytic acyl transfer reagents rather than as Brønsted acid catalysts simply activating acid anhydrides. Remarkably, highly efficient phosphoric acid (1-3 mol %)-catalyzed acylation of alcohols with acid anhydrides was achieved and a 23 g scale synthesis of an ester was demonstrated. Also, phosphoric acid catalyst was effective for synthetically useful esterification from carboxylic acids, alcohols, and acid anhydride. Moreover, with regard to recent developments in chiral 1,1'-bi-2-naphthol (BINOL)-derived phosphoric acid diester catalysts toward asymmetric kinetic resolution of alcohols by acylation, some phosphate diesters were examined. As a result, a ³¹P NMR study and a kinetics study strongly supported not only the acid-base cooperative mechanism as previously proposed by other researchers but also the mixed anhydride mechanism as presently proposed by us.

Runge–Kutta analysis for optimizing the Zn-catalyzed transesterification conditions of MA and MMA with diols to maximize monoesterified products

Terminal hydroxylated acrylate derivatives were prepared by transesterification using zinc catalyst. The time to reach the equilibrium state was analyzed by curve-fitting analysis based on the Runge–Kutta method for optimizing the best conditions.

Facile synthesis of a highly efficient Co/Cu@NC catalyst for base-free oxidation of alcohols to esters

Co/Cu nanoparticle co-decorated N-doped carbon exhibits excellent activity and stability for base-free oxidation of alcohols to esters.

Single-chain crosslinked polymers via the transesterification of folded polymers: from efficient synthesis to crystallinity control

Herein we report efficient synthetic systems of single-chain crosslinked polymers via the intramolecular transesterification of folded random copolymers in organic media and the unique crystallization behavior of their crosslinked polymers.

Amide–imine conjugate involving gallic acid and naphthalene for nano-molar detection, enrichment and cancer cell imaging of La3+: studies on the catalytic activity of the La3+ complex

A single crystal X-ray structurally characterized amide–imine conjugate (GAN) derived from gallic acid and naphthalene selectively recognizes La³⁺ ion via TURN ON fluorescence through ESIPT and CHEF mechanisms.

Base-catalyzed selective esterification of alcohols with unactivated esters

A practical and efficient base-catalyzed esterification has been developed for the facile synthesis of a broad range of esters from simple alcohols with unactivated tert-butyl esters. This protocol could be conducted at mild conditions, providing esters in high to excellent yields with good functional tolerance. Mechanistic studies provided evidence of an exchange of the tert-butyl alkoxide metal with the alcohol, producing a new alkoxide to participate in the transesterification reaction.

Acrylate-Selective Transesterification of Methacrylate/Acrylate Copolymers: Postfunctionalization with Common Acrylates and Alcohols

Acrylate-selective transesterification of methacrylate/acrylate copolymers with alcohols was developed for a site-selective postfunctionalization technique of polymers without using specific monomers. Importantly, a common methyl acrylate efficiently works as a selective modification unit via transesterification coupled with a titanium alkoxide catalyst. The acrylate-selective transesterification is achieved owing to less steric hindrance of the carbonyl groups that are attached to the main chain without an α-methyl group. Typically, the acrylate pendants of dodecyl methacrylate/methyl acrylate (MA) random copolymers were selectively transesterified with benzyl alcohol (BzOH). The conversion of the pendent esters into benzyl esters proportionally increased with MA contents. Additionally, various alcohols were applicable to this MA-selective transesterification system.

Efficient O-Acylation of Alcohols and Phenol Using Cp2TiCl as a Reaction Promoter

A method has been developed for the conversion of primary, secondary, and tertiary alcohols, and phenol, into the corresponding esters at room temperature. The method uses a titanium(III) species generated from a substoichiometric amount of titanocene dichloride together with manganese(0) as a reductant, as well as methylene diiodide. It involves a transesterification from an ethyl ester, or a reaction with an acyl chloride. A radical mechanism is proposed for these transformations.

Chemo- and Regioselective Direct Functional Group Installation through Catalytic Hydroxy Group Selective Conjugate Addition of Amino Alcohols to α,β-Unsaturated Sulfonyl Compounds

A chemoselective functional group installation through catalytic hydroxy group selective conjugate addition of amino alcohols to a variety of functionalized α,β-unsaturated sulfonyl derivatives was developed. Azide group installation for click chemistry and facile fluorescent labeling onto the less reactive hydroxy group demonstrated the synthetic utility of the present chemoselective catalysis. Moreover, chemo- and regioselective reaction of an unprotected amino diol was achieved for the first time.

K2CO3-promoted formation of aryl esters from primary aryl amides by the acyl-acyl exchange process

A new acyl-acyl exchange reaction has been developed for the formation of aryl esters from primary aryl amides. The reaction could occur under mild reaction conditions with catalytic quantities of K2CO3, and could afford moderate to good yields of the desired products.

Synthesis of esters via sp3 C–H functionalisation

This review describes various methods for the synthesis of eleven classes of esters involving sp³ C–H functionalisation.

Solvent strategy for unleashing the Lewis acidity of titanocene dichloride for rapid Mannich reactions

The remarkable activation effect of alcohol solvent on kinetically inert titanocene dichloride was found to promote rapid three-component Mannich reactions.

On the understanding of BF3·Et2O-promoted intra- and intermolecular amination and oxygenation of unfunctionalized olefins

BF₃·Et₂O was found to be effective for the amination and oxygenation of unfunctionalized olefins. In the presence of 3 equiv. of BF₃·Et₂O, intra- and intermolecular amination and oxygenation reactions could be realized in up to 99% isolated yields.

Direct oxidative esterification of alcohols and hydration of nitriles catalyzed by a reusable silver nanoparticle grafted onto mesoporous polymelamine formaldehyde (AgNPs@mPMF)

Oxidative esterification and hydration of nitriles are catalyzed by a newly synthesized AgNPs@mPMF. The catalyst is well characterized and reusable.

Synchronized Tandem Catalysis of Living Radical Polymerization and Transesterification: Methacrylate Gradient Copolymers with Extremely Broad Glass Transition Temperature

Gradient copolymers with differential sequences linearly changing from methyl methacrylate (MMA) to dodecyl methacrylate (DMA) were efficiently synthesized by a concurrent tandem catalysis in the ruthenium-catalyzed living radical (co)polymerization coupled with the in situ transesterification of MMA with 1-dodecanol assisted by titanium isopropoxide [Ti(Oi-Pr)₄]. The key is to perfectly synchronize the two reactions throughout the tandem catalysis by using molecular sieves (MSs), which facilitates the MMA transesterification into DMA by removing the resulting methanol. The MMA/DMA gradient copolymers had an extremely broad glass transition temperature range (i.e., hardly detectable by differential scanning calorimetry (DSC)), in sharp contrast to the random and the block counterparts of similar compositions.