Cinchona-derived thiourea catalyzed hydrophosphonylation of ketimines—an enantioselective synthesis of α-amino phosphonates

Synthetic Methods for Azaheterocyclic Phosphonates and Their Biological Activity: An Update 2004-2024

The increasing importance of azaheterocyclic phosphonates in the agrochemical, synthetic, and medicinal field has provoked an intense search in the development of synthetic routes for obtaining novel members of this family of compounds. This updated review covers methodologies established since 2004, focusing on the synthesis of azaheterocyclic phosphonates, of which the phosphonate moiety is directly substituted onto to the azaheterocyclic structure. Emphasizing recent advances, this review classifies newly developed synthetic approaches according to the ring size and providing information on biological activities whenever available. Furthermore, this review summarizes information on various methods for the formation of C-P bonds, examining sustainable approaches such as the Michaelis-Arbuzov reaction, the Michaelis-Becker reaction, the Pudovik reaction, the Hirao coupling, and the Kabachnik-Fields reaction. After analyzing the biological activities and applications of azaheterocyclic phosphonates investigated in recent years, a predominant focus on the evaluation of these compounds as anticancer agents is evident. Furthermore, emerging applications underline the versatility and potential of these compounds, highlighting the need for continued research on synthetic methods to expand this interesting family.

Recent Advances in Greener Asymmetric Organocatalysis Using Bio-Based Solvents

Efficient synthetic methods that avoid the extensive use of hazardous reagents and solvents, as well as harsh reaction conditions, have become paramount in the field of organic synthesis. Organocatalysis is notably one of the best tools in building chemical bonds between carbons and carbon-heteroatoms; however, most examples still employ toxic volatile organic solvents. Although a portfolio of greener solvents is now commercially available, only ethyl alcohol, ethyl acetate, 2-methyltetrahydrofuran, supercritical carbon dioxide, ethyl lactate, and diethyl carbonate have been explored with chiral organocatalysts. In this review, the application of these bio-based solvents in asymmetric organocatalytic methods reported in the last decade is discussed, highlighting the proposed mechanism pathway for the transformations.

Сatalytic Asymmetric Synthesis of C-Chiral Phosphonates

The current review is devoted to the achievements in the development of methods for the catalytic asymmetric synthesis of phosphonates containing a chiral center in the side chain. C-chiral phosphonates are widely represented among natural compounds with various biological activities as insecticides, herbicides, antibiotics, and bioregulators. Synthetic representatives of this class have found practical application as biologically active compounds. The review summarizes methods of asymmetric metal complex catalysis and organocatalysis as applied to such reactions as phospha-aldol reaction, two-component and three-component phospha-Mannich reaction, phospha-Michael reaction, as well as hydrogenation of unsaturated phosphonates and phosphine oxides, ketophosphonates, and iminophosphonates. Methods for the asymmetric hydride reduction of C=X phosphonates (X=O, S, NR) are also discussed in detail. The review presents updated literature reports, as well as original research by the author.

Asymmetric Synthesis of Tetrasubstituted α-Aminophosphonic Acid Derivatives

Due to their structural similarity with natural α-amino acids, α-aminophosphonic acid derivatives are known biologically active molecules. In view of the relevance of tetrasubstituted carbons in nature and medicine and the strong dependence of the biological activity of chiral molecules into their absolute configuration, the synthesis of α-aminophosphonates bearing tetrasubstituted carbons in an asymmetric fashion has grown in interest in the past few decades. In the following lines, the existing literatures for the synthesis of optically active tetrasubstituted α-aminophosphonates are summarized, comprising diastereoselective and enantioselective approaches.

Synthesis of α-Aminophosphonates and Related Derivatives; the Last Decade of the Kabachnik-Fields Reaction

The Kabachnik-Fields reaction, comprising the condensation of an amine, oxo compound and a P-reagent (generally a >P(O)H species or trialkyl phosphite), still attracts interest due to the challenging synthetic procedures and the potential biological activity of the resulting α-aminophosphonic derivatives. Following the success of the first part (Molecules 2012, 17, 12821), here we summarize the synthetic developments in this field accumulated in the last decade. The procedures compiled include catalytic accomplishments as well as catalyst-free and/or solvent-free "greener" protocols. The products embrace α-aminophosphonates, α-aminophosphinates, and α-aminophosphine oxides along with different bis derivatives from the double phospha-Mannich approach. The newer developments of the aza-Pudovik reactions are also included.

Enantioselective Reaction of 2H-Azirines

2H-Azirines are useful precursors for the synthesis of a variety of chiral aziridine and amine derivatives with a range of biological activities. Owing to the ring strain and the presence of a C=N double bond, 2H-azirines are more reactive than other types of ketimine, and undergo a range of enantioselective reactions, including reduction and Diels-Alder reactions, as well as nucleophilic addition to the C=N double bond. Therefore, the enantioselective reactions of 2H-azirines has become a hot topic, in particular within the last few years. In this Minireview, we focus on the enantioselective reactions of 2H-azirines by using catalytic or stoichiometric amounts of chiral additives, the reaction mechanisms, and the applications of these reactions of 2H-azirines and related compounds in organic synthesis.

N-Sulfonyl Bisimidazoline Ligands and Their Applications in Pd(II)-Catalyzed Asymmetric Addition toward α-Tertiary Amines

A new class of chiral N-sulfonyl bisimidazoline (Bim) ligands have been designed, prepared, and applied in Pd(II)-catalyzed asymmetric addition of arylboronic acids to isatin-derived N-Boc ketimines. The combination of Pd(OCOCF₃)₂ and N-tosyl Bim ligand shows high catalytic activity and excellent asymmetric induction, enabling asymmetric addition to offer α-tertiary amines with generally good to high yields and excellent enantioselectivity (up to 96% yield, 96% ee). This asymmetric Pd(II) catalysis can tolerate air conditions, providing a practical and operationally simple protocol toward the construction of an enantioenriched α-tertiary stereocenter.

Catalytic synthesis of 3-aminooxindoles via addition to isatin imine: an update

3-Substituted-3-aminooxindoles have attracted the attention of organic chemist to develop different synthetic methodologies for their synthesis using catalysts. This review covers the recent developments.

Enantioselective Hydrophosphonylation of in Situ Generated N-Acyl Ketimines Catalyzed by BINOL-Derived Phosphoric Acid

An efficient route to pharmacologically interesting isoindolinone-based α-amino phosphonates is described via asymmetric hydrophosphonylation of in situ generated ketimines catalyzed by BINOL-derived phosphoric acid. The reaction proceeds smoothly at ambient temperature affording a variety of α-amino phosphonates with a quaternary stereogenic center embedded in isoindolinone motif in high yields with excellent enantiomeric ratios (up to 98.5:1.5 er). Several interesting transformations of the products into valuable synthetic intermediates are also depicted.

Catalytic asymmetric synthesis of hetero-substituted oxindoles

The construction of chiral disubstituted oxindoles is an intriguing challenge for organic chemists.

Effective asymmetric vinylogous Mannich reaction of isatin imines with α,α-dicyanoolefins in the presence of a simple chiral amide phosphonium bifunctional phase transfer catalyst

A Mannich reaction between N-Boc isatin imine and α,α-dicyanoolefin as well as subsequent oxidative cleavage of the malonic nitrile moiety were described.

Enantioselective dearomatization of isoquinolines by anion-binding catalysis en route to cyclic α-aminophosphonates

An enantioselective dearomatization of isoquinolines has been developed using chiral anion-binding catalysis. This transformation makes use of silyl phosphite as a nucleophile and generates cyclic α-aminophosphonates.

An enantioselective dearomatization of isoquinolines has been developed using chiral anion-binding catalysis. This transformation, catalyzed by a simple and easy to prepare tert-leucine-based thiourea derivative, makes use of silyl phosphite as a nucleophile and generates cyclic α-aminophosphonates. This is the first time asymmetric anion-binding catalysis has been applied to the synthesis of α-aminophosphonates.

Enantioselective addition of diphenyl phosphonate to ketimines derived from isatins catalyzed by binaphthyl-modified organocatalysts

Chiral binaphthyl-modified squaramide-catalyzed enantioselective addition of diphenyl phosphonate to ketimines derived from isatins has been achieved. This method affords practical and efficient access to chiral 3-amino-3-phosphonyl-substituted oxindole derivatives in high yields with excellent enantioselectivities (up to 99% ee).

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

Multicomponent reactions (MCRs) are one of the most important processes for the preparation of highly functionalized organic compounds in modern synthetic chemistry. As shown in this review, they play an important role in organophosphorus chemistry where phosphorus reagents are used as substrates for the synthesis of a wide range of phosphorylated heterocycles. In this article, an overview about multicomponent reactions used for the synthesis of heterocyclic compounds bearing a phosphonate group on the ring is given.

Imidazolylpyridine-In(OTf)3 catalyzed enantioselective allylation of ketimines derived from isatins

An enantioselective In(OTf)₃-catalyzed allylation of ketimines derived from isatins in the presence of an imidazolylpyridine ligand is described.

An enantioselective organocatalyzed aza-Morita-Baylis-Hillman reaction of isatin-derived ketimines with acrolein

A highly enantioselective aza-Morita-Baylis-Hillman (aza-MBH) reaction of isatin-derived ketimines with acrolein was established using β-isocupreidine (β-ICD) or α-isocupreine (α-ICPN) as a chiral acid-base organocatalyst. The present protocol readily furnished (S) or (R)-aza-MBH adducts with a chiral tetrasubstituted carbon stereogenic center in up to 98% ee.

Stereoselective synthesis of 3-amino-2-oxindoles from isatin imines: new scaffolds for bioactivity evaluation

3-Substituted-3-aminooxindole motifs constitute the core structure of a number of natural products and drug candidates.

Maleimide as an efficient nucleophilic partner in the aza-Morita–Baylis–Hillman reaction: synthesis of chiral 3-substituted-3-aminooxindoles

A highly enantioselective β-isocupreidine catalyzed aza-Morita–Baylis–Hillman reaction of maleimides with isatin derived ketimines provides 3-substituted-3-aminooxindoles with enantiomeric excess upto 99%.