Efficient Bifunctional Organocatalyst Research Articles

Simultaneous Activation of Carbon Dioxide and Epoxides to Produce Cyclic Carbonates by Cross‐linked Epoxy Resin Organocatalysts

AbstractThe development of efficient bifunctional organocatalysts for the catalytic conversion of CO2under mild conditions remains particularly challenging. Inspired by the synergistic mechanism of intramolecular Lewis acid‐base active sites, we report a series of bifunctional cross‐linked epoxy resin organocatalysts containing multiple active sites for the cycloaddition reaction of dilute CO2with epoxides. These catalysts exhibit high reactivity and product selectivity (10 examples, >99 %) for the cycloaddition reactions of a variety of epoxides and CO2, and surprisingly, epichlorohydrin (ECH), can be converted under ambient temperature and pressure (25 °C, 1.0 bar) without co‐catalysts.1H NMR,13C NMR,19F NMR and in situ IR studies suggest that the simultaneous and efficient activation of CO2and epoxides is responsible for the improved catalytic activity. Upon an insightful investigation of the catalytic mechanism, this protocol will contribute to the development of efficient and environmentally friendly metal‐free catalysts.

Chiral Proline Amide‐Isothiouronium Salt Spaced with Diamine as an Efficient Bifunctional Organocatalyst for Enantioselective α‐Hydrazination of Aldehydes

AbstractThe chiral proline amide‐isothiouronium salt‐based bifunctional organocatalyst was prepared by methylating of the corresponding chiral thiourea, containing more acidic and active N−H bonds compared to thiourea. This catalyst was applied to α‐hydrazination of aldehydes using azodicarboxylates, which can be transformed into β‐hydrazino alcohols, β‐amino alcohols, and α‐amino acid derivatives. Enantioselective α‐hydrazination of aldehydes has been successfully carried out with amide‐isothiouronium salt as a chiral catalyst. Various hydrazino aldehydes were obtained in high to quantitative yields and excellent enantioselectivities (of up to 99 % ee) in the presence of a benzoic acid additive.

Acidic pyridinium ionic liquid: an efficient bifunctional organocatalyst to synthesis carbonate from atmospheric CO2 and epoxide.

Ionic liquids (ILs) are used as non-toxic, biodegradable, non-volatile, and relatively low-cost catalysts to synthesize 5-membered cyclic organic carbonates (COCs) from carbon dioxide (CO2) and different types of oxiranes in great conversion and selectivity. Single-component IL containing pyridinium salt moieties as quaternary amine, the carboxylic functional group as a H-bond donor, and bromine as a nucleophile and significant leaving group was synthesized by a simple method. The simultaneous selection and use of all mentioned factors in IL caused the epoxides converted into their corresponding carbonates under mild conditions, under 1 atm carbon dioxide (CO2) pressure (CO2 balloon), co-catalyst/ metal/ and solvent-free during 2.5 h. The synthetic catalyst converted styrene oxide (SO) to styrene carbonate (SC) with 100% conversion and selectivity. Moreover, the catalyst could be recycled more than four times before losing its remarkable catalytic activity. Finally, an inferential mechanism was suggested according to the experimental results.

Chiral Polyureas Derived Cinchona Alkaloids: Highly Efficient Bifunctional Organocatalysts for the Asymmetric Michael Addition Reaction

AbstractRepetitive Mizoroki‐Heck (MH) coupling polymerization was used to create novel chiral polyureas with cinchona alkaloids in the main chain. Apart from two‐component polycondensation of cinchona urea dimers with diiodobenzene via MH reaction conditions, some chiral polyureas were easily polymerized under self polycondensation to yield the chiral polymers. The asymmetric Michael addition reaction was successfully carried out using chiral polymers derived cinchona urea. Interestingly, phenolic‐based chiral polymers served as heterogeneous catalysts for the enantioselective Michael reaction, with high catalytic activity and excellent enantioselectivities (up to 99 % ee). These polymeric catalysts were also stable, and they could be recycled and reused.

Isothiouronium salt based chiral proline amide as efficient bifunctional organocatalyst for direct asymmetric aldol reactions in aqueous medium

We developed the first chiral proline amide-isothiouronium based bifunctional organocatalyst, it was prepared by methylation of the corresponding thiourea. This asymmetric catalyst provides aldol products in high to quantitative yields while achieving excellent control performance of diastereoselectivities (anti/syn, up to 95:5 dr) and enantioselectivity (up to 99% ee) in the aldol reaction of various benzaldehydes with a cyclohexanone in water and formic acid.

Pyridine-bridged bifunctional organocatalysts for the synthesis of cyclic carbonates from carbon dioxide

Hydroxyl- and carboxyl-functionalized imidazolium halides are used as efficient bifunctional organocatalysts for the synthesis of cyclic carbonates from CO2 and epoxides under mild reaction conditions. Control experiments suggest that the cycloaddition reaction is realized by the combination of the nucleophilic halide anions with hydroxyl and carboxyl groups as hydrogen bond donors. Moreover, the bifunctional organocatalysts can be easily recycled five times by simple filtration; however, a loss of activity was observed.

An Electrostatically Enhanced Phenol as a Simple and Efficient Bifunctional Organocatalyst for Carbon Dioxide Fixation.

An electrostatically enhanced phenol as a simple and competent bifunctional organocatalyst for the atom-economical conversion of epoxides to cyclic carbonates under environmentally benign conditions is described. Incorporating a positively charged center into phenols through a modular one-step synthesis results in a bifunctional system with enhanced acidity and reactivity, capable of epoxide activation, a halide nucleophilic ring-opening process, and CO2 incorporation in a synergistic fashion. A rational survey of the efficiency of different positively charged phenols and the influence of different parameters, such as temperature, catalyst loading, and the nature of the nucleophile, on catalytic activity was conducted. In addition, the time-dependent conversion of epoxide into the corresponding cyclic carbonate was further explored by FTIR-ATR and 1 H NMR spectroscopy. This bifunctional catalytic platform is among one of the mildest and most efficient metal-free systems that is capable of converting a variety of epoxides into cyclic carbonates under virtually ambient conditions. The 1 H NMR titration experiment validated the bifunctional catalytic mechanism wherein both the epoxide activation and the nucleophilic ring-opening process occur in concert en route to carbon dioxide fixation.

Chiral N,N'-Dioxide Organocatalyzed Asymmetric Electrophilic α-Cyanation of β-Keto Esters and β-Keto Amides.

An enantioselective electrophilic α-cyanation of 1-indanone-derived β-keto esters and β-keto amides using a hypervalent iodine as the cyanide-transfer reagent was realized. A chiral N,N'-dioxide was used as the efficient bifunctional organocatalyst in the presence of inorganic base, which gave the corresponding α-cyano dicarbonyl compounds in yields of 50-99% with good enantioselectivities (87-97% ee).

Phosphine-boronates: efficient bifunctional organocatalysts for Michael addition

Phosphine-boronates R(2)P(o-C(6)H(4))B(OR')(2) have been evaluated as bifunctional organocatalysts for the Michael addition of malonate pronucleophiles to methylvinylketone. The presence of the Lewis acidic boron center adjacent to phosphorus significantly improves catalytic performance. Isolation and complete characterization of a key intermediate, namely a β-phosphonium enolate, substantiate the role of the Lewis acidic moiety in the catalytic process.

ChemInform Abstract: Highly Efficient Bifunctional Organocatalysts for the Asymmetric Michael Addition of Ketones to Nitroolefins.

AbstractA novel proline derived chiral bis‐amine catalyst is designed and successfully applied to the title process.

Biscinchona alkaloids as highly efficient bifunctional organocatalysts for the asymmetric conjugate addition of malonates to nitroalkenes at ambient temperature

The novel bifunctional bisalkaloids have been developed as highly efficient catalysts for the asymmetric conjugate addition of 1,3-dicarbonyl compounds to nitroalkenes with low catalyst loading (1 mol %) at ambient temperature, providing the products with excellent enantioselectivities (up to 97% ee).

Highly efficient bifunctional organocatalysts for the asymmetric Michael addition of ketones to nitroolefins

A type of secondary–secondary–tertiary triamine bifunctional organocatalysts have been properly designed and synthesized. In our study, the designed catalyst (S)-N-(pyrrolidin-2-ylmethyl)pyridin-2-amine 5 has been shown to be highly efficient to promote the asymmetric Michael addition of ketones to nitroolefins at room temperature, which afforded the corresponding adducts in excellent diastereoselectivities (up to 99:1 dr) and enantioselectivities (up to >99% ee).

ChemInform Abstract: Tropos Biphenol Derived Chiral Thiophosphoramide Catalyzed Highly Diastereo‐ and Enantioselective Michael Addition of Cyclic Ketones to Nitro Olefins.

AbstractThe new thiophosphoramide (I) is used as efficient bifunctional organocatalyst for the asymmetric Michael addition of cyclic ketones to nitro olefins.

Pyrrolidinyl-sulfamide derivatives as a new class of bifunctional organocatalysts for direct asymmetric Michael addition of cyclohexanone to nitroalkenes

A series of chiral pyrrolidinyl-sulfamide derivatives have been identified as efficient bifunctional organocatalysts for the direct Michael addition of cyclohexanone to a wide range of nitroalkenes. The desired Michael adducts were obtained in high chemical yields and excellent stereoselectivities (up to 99/1 dr and 95% ee).

ChemInform Abstract: 4‐Trifluoromethanesulfonamidyl Prolinol tert‐Butyldiphenylsilyl Ether as a Highly Efficient Bifunctional Organocatalyst for Michael Addition of Ketones and Aldehydes to Nitroolefins.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: N‐Tosyl‐(Sa)‐binam‐L‐prolinamide as Highly Efficient Bifunctional Organocatalyst for the General Enantioselective Solvent‐Free Aldol Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether as a highly efficient bifunctional organocatalyst for Michael addition of ketones and aldehydes to nitroolefins

4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether bifunctional organocatalyst 3a is a highly efficient catalyst for the asymmetric Michael addition reactions of ketones and aldehydes to nitrostyrenes, leading to syn-selective adducts with excellent yields (>99%), high diastereoselectivities (up to 99:1 dr) and excellent enantioselectivities (up to 99% ee). Control experiments suggested that the trans-configuration relationship between the bulky group (–CH 2OTBDPS) and the sulfonamido group at the 4-position of the pyrrolidine ring was important to achieve high yield and stereoselectivity.

Amide-based bifunctional organocatalysts in asymmetric reactions

A series of amide-based bifunctional organocatalysts have been utilized in asymmetric reactions. Prolinamide analogues have been designed to catalyze asymmetric reactions via enamine intermediates with the assistance of tunable hydrogen bonding. In addition, the combination of various Lewis base functional groups, such as guanidine, N-oxide and phosphane, with an amide moiety have also constituted efficient bifunctional organocatalysts with unique reactivity and selectivity.

N-Tosyl-(Sa)-binam-l-prolinamide as Highly Efficient Bifunctional Organocatalyst for the General Enantioselective Solvent-Free Aldol Reaction

This work was financially supported by the Direccion General de Investigacion of the Ministerio de Educacion y Ciencia of Spain (Proyects CTQ2007-62771/BQU and Consolider Ingenio 2010 CSD2007-00006), and the University of Alicante (GRJ06-05).

Noyori’s Ts-DPEN ligand: an efficient bifunctional primary amine-based organocatalyst in enantio- and diastereoselective Michael addition of 1,3-dicarbonyl indane compounds to nitroolefins

Noyori’s Ts-DPEN ligand bearing an amino sulfonamide moiety and with a primary amino group on a chiral scaffold was found to be a simple and efficient bifunctional organocatalyst for the asymmetric Michael addition of 1,3-dicarbonyl compounds to nitroolefins, which gave highly functional Michael adduct with quaternary stereocenters in good enantioselectivities (up to 84%ee) and dr (up to 5.7:1 dr).