Chiral Heterodisulfoxide Ligands in Rhodium-Catalyzed Asymmetric 1,4-Addition of Arylboronic Acids to Chromenones

Transition Metal-Catalyzed Enantioselective Synthesis of Chiral Five- and Six-Membered Benzo O-heterocycles

Enantiomerically enriched five- and six-membered benzo oxygen heterocycles are privileged architectures in functional organic molecules. Over the last several years, many effective methods have been established to access these compounds. However, comprehensive documents cover updated methodologies still in highly demand. In this review, recent transition metal catalyzed transformations lead to chiral five- and six-membered benzo oxygen heterocycles are presented. The mechanism and chirality transfer or control processes are also discussed in details.

Recent Developments on Photochemical Synthesis of 1,n-Dicarbonyls

1,n-dicarbonyls are one of the most fascinating chemical feedstocks finding abundant usage in the field of pharmaceuticals. Besides, they are utilized in a plethora of synthesis in general synthetic organic chemistry. A number of 'conventional' methods are available for their synthesis, such as the Stetter reaction, Baker-Venkatraman rearrangement, oxidation of vicinal diols, and oxidation of deoxybenzoins, synonymous with unfriendly reagents and conditions. In the last 15 years or so, photocatalysis has taken the world of synthetic organic chemistry by a remarkable renaissance. It is fair to say now that everybody loves the light and photoredox chemistry has opened a new gateway to organic chemists towards milder, more simpler alternatives to the previously available methods, allowing access to many sensitive reactions and products. In this review, we present the readers with the photochemical synthesis of a variety of 1,n-dicarbonyls. Diverse photocatalytic pathways to these fascinating molecules have been discussed, placing special emphasis on the mechanisms, giving the reader an opportunity to find all these significant developments in one place.

Asymmetric Synthesis of Sakuranetin-Relevant Flavanones for the Identification of New Chiral Antifungal Leads

Discovery and efficient synthesis of new promising leads have a central role in agrochemical science. Reported herein is the sakuranetin-directed synergistic exploration of an asymmetric synthesis and an antifungal evaluation of chiral flavanones. A new palladium catalytic system with CarOx-type ligands was successfully identified for the highly enantioselective addition of arylboronic acids to chromones. This enabled the facile and programmable construction of a constellation of chiral flavanones (up to 98% yield and 97% ee), in which (R)-pinostrobin was efficiently constructed without laborious protecting/deprotecting operations. Its good performance in asymmetric induction and functional tolerance expanded the chemical space of pharmaceutically important flavanones. The chiral differentiation of flavanones based on antifungal activity and a concise structure-activity relationship model was disclosed and summarized. This synergistic project culminated with acquisition of the naturally unprecedented flavanones with better antifungal potentials than sakuranetin, in which the R-enantiomer of flavanone 54 (EC₅₀ = 0.8 μM) demonstrated better performance than boscalid against Rhizoctonia solani. The novel scaffold and predicted new target compared with the commercial fungicides in the FRAC reinforce the value of further exploration.

Enantiopure ferrocene-1,2-disulfoxides: synthesis and reactivity

The rational use of directed deprotometallation, sulfur oxidation and sulfoxide/lithium exchange allowed the synthesis of enantiopure ferrocene-1,2-disulfoxide derivatives. Not only do they represent the first members of this original family, but some of them have shown promise as ligands in rhodium-catalysed conjugate addition.

Catalytic enantioselective synthesis of tetrasubstituted chromanones via palladium-catalyzed asymmetric conjugate arylation using chiral pyridine-dihydroisoquinoline ligands

Highly enantioselective conjugate addition reactions of arylboronic acids to 2-substituted chromones catalyzed by palladium complexes with new chiral Pyridine-Dihydroisoquinoline (PyDHIQ) ligands have been developed. These reactions provide highly enantioselective access to chromanones containing tetrasubstituted stereocenters. Various arylboronic acids and 2-substituted chromones can be used in the catalytic reaction to afford the chiral tetrasubstituted chromanones in good yields and excellent enantioselectivities (25 examples, up to 98% yields, up to 99% ee).

Silver-Catalyzed Radical Cascade Cyclization toward 1,5-/1,3-Dicarbonyl Heterocycles: An Atom-/Step-Economical Strategy Leading to Chromenopyridines and Isoxazole-/Pyrazole-Containing Chroman-4-Ones

A novel and convenient silver-catalyzed radical cascade cyclization toward a large variety of 1,5-/1,3-dicarbonyl heterocycles containing a chroman-4-one, indanone, or 2,3-dihydroquinolin-4(1 H)-one moiety was developed, by reacting various 2-functionalized benzaldehydes, including 2-allyloxy benzaldehydes, 2-allyl benzaldehyde, and 2-N(Ts)CH₂-CH═CH₂ substituted benzaldehyde, with 1,3-dicarbonyl compounds in the presence of AgNO₃/K₂S₂O₈ in one pot under mild reaction conditions. The newly obtained 1,5-/1,3-dicarbonyl-containing heterocycles were further used directly to synthesize more structurally diverse polyheterocycles, mainly including chromenopyridines as well as isoxazole- or pyrazole-containing chroman-4-ones.

Chiral Organosulfur Ligands/Catalysts with a Stereogenic Sulfur Atom: Applications in Asymmetric Synthesis

Asymmetric synthesis, in which chiral organocatalysts or metal complexes with chiral ligands are used, has become the most valuable methodology for the preparation of enantiomerically pure organic compounds. Among such catalysts/ligands, a growing number constitute various organosulfur compounds. This Review provides comprehensive and critical information on the plethora of sulfur-based chiral ligands and organocatalysts used in asymmetric synthesis, which have been published within the last 15 years. However, it is confined to the presentation of only those chiral catalysts/ligands that possess a stereogenic sulfur atom and includes sulfoxides, sulfinamides, N-sulfinyl ureas, sulfoximines, and some related S-chiral derivatives.

A highly enantioselective access to chiral chromanones and thiochromanones via copper-catalyzed asymmetric conjugated reduction of chromones and thiochromones

The chromanone scaffold is a privileged structure in heterocyclic chemistry and drug discovery.

Palladium-Catalyzed Asymmetric Conjugate Addition of Arylboronic Acids to α,β-Unsaturated Cyclic Electrophiles

This account describes our laboratory's efforts in the development of a palladium-catalyzed asymmetric conjugate addition of arylboronic acids to cyclic conjugate acceptors. Specifically, we highlight the study of this transformation in the following areas: (a) construction of all-carbon quaternary stereocenters, (b) elucidation of the reaction mechanism,

The emergence of sulfoxides as efficient ligands in transition metal catalysis

Sulfoxides are capable of forming stable complexes with transition metals and there have been many comprehensive studies into their binding properties. However, the use of sulfoxides, particularly chiral sulfoxides, as ligands in transition metal catalysis is rather less well developed. This review aims to describe these catalytic studies and covers new developments that are showing very promising results and that have led to a renewed interest in this field.

Computational modelling of the enantioselectivity in the asymmetric 1,4-addition reaction catalyzed by a Rh complex of a S-chiral disulfoxide

Computational chemistry is a powerful tool for understanding chiral catalysis and can also aid future catalyst design.

Palladium-catalyzed asymmetric conjugate addition of arylboronic acids to heterocyclic acceptors

Flava Flavanone: Asymmetric conjugate additions to chromones and 4-quinolones are reported utilizing a single catalyst system formed in situ from Pd(OCOCF(3))(2) and (S)-tBuPyOX. Notably, these reactions are performed in wet solvent under ambient atmosphere, and employ readily available arylboronic acids as the nucleophile, thus providing ready access to these asymmetric heterocycles (see scheme).

Enantioselective total synthesis of (+)-lithospermic acid

An enantioselective synthesis of (+)-lithospermic acid, a potent anti-HIV agent, has been accomplished in a convergent manner in nine steps. The synthesis features an enantioselective intramolecular oxa-Michael addition catalyzed by a quinidine derivative, a hypervalent iodine-mediated rearrangement of chromanone to dihydrobenzofuran, an enantioselective α-oxyamination, and an intermolecular C-H olefination.