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article

Phosphoric acid mediated tautomerism of imines: addition of a secondary enamine intermediate to aldehydes

Lindsey O. Davis, Marcella A. Putri, Caitlin L. Meyer, Christopher P. Durant, more

Tetrahedron Letters > 2014 > 55 > 19 > 3100-3103

A phosphoric acid derivative has been shown to promote the addition between an imine and several aldehyde substrates through an enamine intermediate to give cross-aldol condensation products. The reaction scope and preliminary mechanistic investigations will be presented.

article

Organocatalytic asymmetric Friedel–Crafts reaction of 1-naphthols with isatins: an enantioselective synthesis of 3-aryl-3-hydroxy-2-oxindoles

Jasneet Kaur, Akshay Kumar, Swapandeep Singh Chimni, J. Kaur, more

Tetrahedron Letters > 2014 > 55 > 13 > 2138-2141

An organocatalytic enantioselective Friedel–Crafts reaction of 1-naphthols with isatins has been developed employing bifunctional thiourea–tertiary amine organocatalysts. A variety of isatin derivatives react well with 1-naphthols in the presence of Cinchona derived thiourea 1a to provide biologically important chiral 3-aryl-3-hydroxy-2-oxindoles (3a–zg) in good yield (70–84%) and moderate to good...

article

Quinine as an organocatalytic dual activator for the diastereoselective synthesis of spiro-epoxyoxindoles

Mangilal Chouhan, Anang Pal, Ratnesh Sharma, Vipin A. Nair, more

Tetrahedron Letters > 2013 > 54 > 52 > 7119-7123

A highly efficient organocatalytic approach has been developed for the diastereoselective epoxidation of (E)-3-ylidene-indolin-2-one derivatives using readily available natural product quinine and urea-hydrogen peroxide (UHP) in DCM at 10°C to afford trans spiro-epoxyoxindoles which were further utilized to obtain β-hydroxy-α-amino esters by water mediated regioselective ring opening from the less...

article

Recyclable cinchona alkaloid catalyzed asymmetric Michael addition reaction

Xin Huang, Wen-Bin Yi, Danash Ahad, Wei Zhang, more

Tetrahedron Letters > 2013 > 54 > 45 > 6064-6066

A highly enantioselective and diastereoselective Michael addition reaction of α-fluoro-β-ketoesters with maleimides is catalyzed by fluorous cinchona alkaloid to afford two adjacent chiral centers. The catalyst attached with a perfluroalkyl tag can be recovered by fluorous solid-phase extraction (F-SPE).

article

Recyclable Polythioesters and Poly(thioester‐co‐peptoid)s via Ring‐Opening Cascade Polymerization of Amino Acid N‐Carboxyanhydrides

Shuo Wang, Zi‐You Tian, Hua Lu

Angewandte Chemie > 136 > 45 > n/a - n/a

Polythioesters (PTEs) are emerging sustainable polymers for their degradability and recyclability. However, low polymerizability of monomers and extensive side reactions often hampered the polymerization process. Moreover, copolymers containing both thioester and other types of functional groups in the backbone are highly desirable but rarely accomplished owing to several synthetic challenges. Here,...

article

Recyclable Polythioesters and Poly(thioester‐co‐peptoid)s via Ring‐Opening Cascade Polymerization of Amino Acid N‐Carboxyanhydrides

Shuo Wang, Zi‐You Tian, Hua Lu

Angewandte Chemie International Edition > 63 > 45 > n/a - n/a

Polythioesters (PTEs) are emerging sustainable polymers for their degradability and recyclability. However, low polymerizability of monomers and extensive side reactions often hampered the polymerization process. Moreover, copolymers containing both thioester and other types of functional groups in the backbone are highly desirable but rarely accomplished owing to several synthetic challenges. Here,...

article

Fluorinated Chiral Pyrans Obtained via Mechanochemical Organocatalytic Michael/oxa‐Michael Cascade

Klára Stankovianska, Viktória Némethová, Tibor Peňaška, Jakub Borko, more

European Journal of Organic Chemistry > 27 > 38 > n/a - n/a

Fluorine‐containing compounds are important in medicine or crop‐protection. Herein, we show asymmetric organocatalytic Michael/oxa‐Michael cascade leading to chiral fluorinated pyrans under mechanochemical conditions. Formal oxa‐Diels‐Alder reaction between fluorine containing unsaturated keto esters and β,γ‐unsaturated ketones afforded a range of drug‐like pyran derivatives in short times and good...

article

Enantioselective (3+2) Annulation of Donor‐Acceptor Cyclopropanes with Aldehydes and Ketones Catalyzed by Brønsted Bases

Erlaitz B. Obregón, Louise G. Rost, Ida R. Kocemba, Anne Kristensen, more

Angewandte Chemie International Edition > 63 > 42 > n/a - n/a

The substituted tetrahydrofuran core is a structural motif in many biologically active and natural compounds. However, the scarcity of enantioselective methods developed towards its synthesis makes this field challenging and attractive to explore. Herein, the first Brønsted‐base catalyzed enantioselective (3+2) annulation of donor‐acceptor cyclopropanes with aldehydes and ketones affording enantioenriched...

article

Enantioselective (3+2) Annulation of Donor‐Acceptor Cyclopropanes with Aldehydes and Ketones Catalyzed by Brønsted Bases

Erlaitz B. Obregón, Louise G. Rost, Ida R. Kocemba, Anne Kristensen, more

Angewandte Chemie > 136 > 42 > n/a - n/a

The substituted tetrahydrofuran core is a structural motif in many biologically active and natural compounds. However, the scarcity of enantioselective methods developed towards its synthesis makes this field challenging and attractive to explore. Herein, the first Brønsted‐base catalyzed enantioselective (3+2) annulation of donor‐acceptor cyclopropanes with aldehydes and ketones affording enantioenriched...

article

Organocatalyzed Approach to the Synthesis of γ‐Pyrones via Hydration/Cyclization of Skipped Diynones under Basic Conditions

Elisavet‐Maria Zantioti‐Chatzouda, Nikolaos Koromilas, Vasiliki Kotzabasaki, Emmanouil Kosidekakis, more

European Journal of Organic Chemistry > 27 > 37 > n/a - n/a

In the presence of catalytic amounts of a secondary amine (e. g. morpholine), skipped diynones undergo hydration/cyclization in aqueous acetonitrile to form γ‐pyrones in moderate to excellent yields (30–92 %). The first step of the process involves a trans‐stereoselective conjugate‐addition of morpholine to the ynone to form an intermediate E‐enaminone. Gradually this intermediate reacts with H₂O...

article

Organocatalysis for Enantioselective Decarboxylative Nucleophilic Addition Reactions

Naoki Yasukawa, Shuichi Nakamura

European Journal of Organic Chemistry > 27 > 35 > n/a - n/a

The catalytic decarboxylation of malonic acid half oxy‐ and thioesters, β‐ketocarboxylic acids, and their related compounds is a straightforward, powerful, and atom‐economical strategy for the in‐situ formation of enolates, which are important and well‐studied synthons for various functional materials and natural products. This strategy, inspired by the biosynthesis of polyketides and fatty acids,...

article

Organocatalytic Activation of Unsymmetrical 2,3‐Diketones Towards Catalytic Asymmetric Domino Michael–Henry Reaction

Łukasz Adam Włoszczak, Marcin Górecki, Jacek Mlynarski

European Journal of Organic Chemistry > 27 > 35 > n/a - n/a

In this study, we explored a method to distinguish between both enolizable regions of unsymmetrical 2,3‐diketones in organocatalytic domino reactions involving nitroalkenes. The selective formation of an enamine from only one side of the molecule was made possible by the use of optically pure 2‐(trifluoromethyl)pyrrolidine. This catalyst, remarkably enhancing the reaction, owes its efficacy to a unique...

article

N‐Heterocyclic Carbene/Transition Metal Dual Catalysis

Zhao‐Fei Zhang, Chun‐Lin Zhang, Song Ye

Chemistry – A European Journal > 30 > 54 > n/a - n/a

N‐heterocyclic carbene catalysis has been developed as a versatile method for the enantioselective synthesis of complex organic molecules in organic chemistry. Merging of N‐heterocyclic carbene catalysis with transition metal catalysis holds the potential to achieve unprecedented transformations with broad substrate scope and excellent stereoselectivity, which are unfeasible with individual catalyst...

article

Binary Catalytic Hydrogen/Deuterium Exchange of Free α‐Amino Acids and Derivatives

Guorong Xiao, Hong Sun, Gege Jiang, Ying Liu, more

Chemistry – A European Journal > 30 > 52 > n/a - n/a

The increasing demand for deuterium‐labeled amino acids and derivatives has heightened interest in direct hydrogen/deuterium exchange reactions of free amino acids. Existing methods, including biocatalysis and metal catalysis, typically require expensive deuterium sources or excessive use of deuterium reagents and often struggle with site selectivity. In contrast, this binary catalysis system, employing...

article

Catalytic Performance of Chiral Tetraaza‐Bridged Calix[4]arene[2]triazine Derivatives for Enantioselective Michael Reactions

Ummu Ozgun, Hayriye Nevin Genc

Chirality > 36 > 9 > n/a - n/a

Novel chiral tetraaza‐bridged calix[4]arene[2]triazine‐based organocatalysts were synthesized and used for catalytic asymmetric Michael reaction of acetylacetone to various aromatic nitrostyrenes. Chiral subunits (R)‐ and (S)‐1,2,3,4‐tetrahydro‐1‐naphthylamine were attached to the tetraaza‐bridged calix[4]arene[2]triazine platform in both enantiomeric forms. The R configuration of the major enantiomer...

article

Recent Advances in the Enantioselective Construction of gem‐Difluorinated Carbonyl Moieties

Xin Li, Qiuling Song

Advanced Synthesis & Catalysis > 366 > 16 > 3405 - 3416

The enantioselective introduction of gem‐difluorinated carbonyl (i. e. α,α‐difluoro carbonyl) moieties into organic structures is a synthetically valuable but highly challenging approach. During the past decades, continuous efforts have been made for the developments of synthetic strategies for constructing C(sp³)−CF₂COR chiral centers with high levels of enantioselectivities. This review summarizes...

article

N‐Heterocyclic Carbene Enabled Functionalization of Inert C(Sp³)−H Bonds via Hydrogen Atom Transfer (HAT) Processes

Fengfei Lu, Fen Su, Shijie Pan, Xiuli Wu, more

Chemistry – A European Journal > 30 > 47 > n/a - n/a

Developing methods to directly transform C(sp³) −H bonds is crucial in synthetic chemistry due to their prevalence in various organic compounds. While conventional protocols have largely relied on transition metal catalysis, recent advancements in organocatalysis, particularly with radical NHC catalysis have sparked interest in the direct functionalization of “inert” C(sp³) −H bonds for cross C−C...

article

Organocatalytic Diastereo‐ and Enantioselective Michael Addition of α‐Aryl Isocyanoacetates to Aurone‐Derived Azadienes

Adrián Laviós, Amparo Sanz‐Marco, Carlos Vila, Gonzalo Blay

European Journal of Organic Chemistry > 27 > 31 > n/a - n/a

A highly diastereo‐ and enantioselective organocatalytic Michael addition of α‐aryl isocyanoacetates to aurone‐derived azadienes under mild conditions has been developed. This efficient methodology enables access to chiral α,α‐disubstituted α‐amino ester derivatives with two adjacent stereocenters, one of them quaternary, bearing a benzofuran scaffold in their structure in high yields and stereocontrol...

article

Organocatalytic Asymmetric Decarboxylative Mannich Reaction for the Synthesis of Non‐Natural α‐Amino Acids Bearing Alkynyl Groups

Xueting Xu, Shengyi Tu, Jiani Sun, Xuehe Lu, more

Advanced Synthesis & Catalysis > 366 > 15 > 3251 - 3256

Asymmetric decarboxylative Mannich addition of β‐keto acids or malonic acid half‐esters to β,γ‐alkynyl‐α‐ketimino esters catalyzed by cinchona alkaloid‐derived squaramide has been developed. The reaction proceeded by forming a nucleophilic enolate after decarboxylation, followed by its addition to β,γ‐alkynyl‐α‐ketimino esters facilitated by the bifunctional catalyst. A broad range of substrates with...

article

Is the E/Z Iminium Ratio a Good Enantioselectivity Predictor in Iminium Catalysis?

Matthijs A. Hellinghuizen, Pietro Franceschi, Jana Roithová

Chemistry – A European Journal > 30 > 46 > n/a - n/a

Developing new enantioselective reactions is an important part of chemical discovery but requires time and resources to test large arrays of potential reaction conditions. New techniques are required to analyse many different reactions quickly and efficiently. Mass spectrometry is a high‐throughput method; when combined with ion‐mobility spectrometry, this technique can monitor diastereomeric reaction...

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Search results

Phosphoric acid mediated tautomerism of imines: addition of a secondary enamine intermediate to aldehydes

Organocatalytic asymmetric Friedel–Crafts reaction of 1-naphthols with isatins: an enantioselective synthesis of 3-aryl-3-hydroxy-2-oxindoles

Quinine as an organocatalytic dual activator for the diastereoselective synthesis of spiro-epoxyoxindoles

Recyclable cinchona alkaloid catalyzed asymmetric Michael addition reaction

Recyclable Polythioesters and Poly(thioester‐co‐peptoid)s via Ring‐Opening Cascade Polymerization of Amino Acid N‐Carboxyanhydrides

Recyclable Polythioesters and Poly(thioester‐co‐peptoid)s via Ring‐Opening Cascade Polymerization of Amino Acid N‐Carboxyanhydrides

Fluorinated Chiral Pyrans Obtained via Mechanochemical Organocatalytic Michael/oxa‐Michael Cascade

Enantioselective (3+2) Annulation of Donor‐Acceptor Cyclopropanes with Aldehydes and Ketones Catalyzed by Brønsted Bases

Enantioselective (3+2) Annulation of Donor‐Acceptor Cyclopropanes with Aldehydes and Ketones Catalyzed by Brønsted Bases

Organocatalyzed Approach to the Synthesis of γ‐Pyrones via Hydration/Cyclization of Skipped Diynones under Basic Conditions

Organocatalysis for Enantioselective Decarboxylative Nucleophilic Addition Reactions

Organocatalytic Activation of Unsymmetrical 2,3‐Diketones Towards Catalytic Asymmetric Domino Michael–Henry Reaction

N‐Heterocyclic Carbene/Transition Metal Dual Catalysis

Binary Catalytic Hydrogen/Deuterium Exchange of Free α‐Amino Acids and Derivatives

Catalytic Performance of Chiral Tetraaza‐Bridged Calix[4]arene[2]triazine Derivatives for Enantioselective Michael Reactions

Recent Advances in the Enantioselective Construction of gem‐Difluorinated Carbonyl Moieties

N‐Heterocyclic Carbene Enabled Functionalization of Inert C(Sp³)−H Bonds via Hydrogen Atom Transfer (HAT) Processes

Organocatalytic Diastereo‐ and Enantioselective Michael Addition of α‐Aryl Isocyanoacetates to Aurone‐Derived Azadienes

Organocatalytic Asymmetric Decarboxylative Mannich Reaction for the Synthesis of Non‐Natural α‐Amino Acids Bearing Alkynyl Groups

Is the E/Z Iminium Ratio a Good Enantioselectivity Predictor in Iminium Catalysis?

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