C(sp)-H Acylation of Benzo[h]quinolines at Room Temperature via Aldehyde Autoxidation and Palladium Catalysis Cooperation.

Herein, we report Pd-catalyzed C(sp)-H acylation using aldehyde as acyl source and O as the green oxidant at room temperature. A selective association of acyl radical formed in-situ during aldehyde autoxidation with Pd-catalysis is the key to the process. The reaction afforded products in good yields (up to 82 %) and it is scalable.

Asymmetric Synthesis of Benzofuranones with a C3 Quaternary Center via an Addition/Cyclization Cascade Using Noncovalent N-Heterocyclic Carbene Catalysis.

An asymmetric addition/cyclization cascade of amidoesters and iminoquinones is developed using noncovalent N-heterocyclic carbene (NHC) catalysis. The process enables access to various functionalized benzofuranones with an all-carbon quaternary stereocenter with high yields and ee values. The reaction displays a broad substrate scope.

Photocatalytic Synthesis of β-Keto Primary Chlorides by Selective Chlorocarbonylation of Olefins.

Functionalized primary alkyl chlorides are precursors to a plethora of scaffolds but their access from chemical feedstocks remains challenging. Herein, we report a concise dual Ni/photoredox catalytic protocol for regioselective chlorocarbonylation of unactivated alkenes that enables rapid access to β-keto primary chlorides. The catalytic process features an extensive substrate scope, scalability and functional group tolerance.

Enantioselective Amination of 3-Substituted-2-benzofuranones via Non-covalent N-Heterocyclic Carbene Catalysis.

Herein, an efficient method for asymmetric α-amination of 2-benzofuranones with N-heterocyclic carbene (NHC) catalysis is reported. The process is based on non-covalent interaction of NHC with substrate, facilitating the formation of a chiral ion-pair that encompasses enolate and azolium salt. The activated enolate adds to an electrophilic amine source with sufficient facial control to furnish an enantioenriched product having an amine substituted quaternary stereocenter.

Photochemical Oximesulfonylation of Alkenes Using Sulfonyl-Oxime-Ethers as Bifunctional Reagents.

Utilization of oxime ethers as bifunctional reagents remains unknown. Herein, we present a mechanistically distinct strategy that enables oximesulfonylation of olefins using sulfonyl-oxime-ethers as bifunctional reagents under metal-free photochemical conditions. Via concomitant C-S and C-C bond formation, the process permits incorporation of oxime and sulfonyl groups into olefins in a complete atom-economic fashion, providing rapid access to multi-functionalized β-sulfonyl oxime ethers with good yields and stereoselectivity.

Brønsted Acid-Promoted Intermolecular Dearomative Photocycloaddition of Bicyclic Azaarenes with Olefins under Aerobic Conditions.

Herein, we present a simplified reaction protocol for the dearomatization of bicyclic azaarenes via photochemical cycloaddition with alkenes using an Ir(III) photosensitizer, trifluoroacetic acid (TFA), dichloroethane, and a blue light-emitting diode. An efficient protonation of azaarenes with TFA enhances the reactivity of triplet azaarene toward olefins, enabling the photocycloaddition under aerobic conditions. The protocol applies to a broad range of substrates.

N-Heterocyclic carbene catalyzed desymmetrization of diols: access to enantioenriched oxindoles having a C3-quaternary stereocenter.

Herein, we describe an effective strategy for enantioselective synthesis of oxindoles having a C3-quaternary stereocenter N-heterocyclic carbene (NHC) catalyzed desymmetrization of diols. The process is based on the catalytic asymmetric transfer acylation of primary alcohols using readily available aldehydes as an acylation agent. The reaction enables easy access to diversely functionalized C3-quaternary oxindoles with excellent enantioselectivity.

Asymmetric Aminative Dearomatization of 2-Naphthols via Non-covalent N-Heterocyclic Carbene Catalysis.

Herein, successful utilization of non-covalent N-heterocyclic carbene (NHC) catalysis toward asymmetric aminative dearomatization of naphthols is presented. The NHC-catalyzed process offers enantioselective synthesis of cyclic enones possessing a nitrogen-containing α-quaternary stereocenter. The reaction applies to various functionalized substrates including acid-labile groups and is shown to be scalable.

Photocatalytic Incorporation of an Oxime Ether Functional Group at Inert C(sp)-H Bonds via HAT.

Herein, we describe a photocatalytic method for the direct incorporation of an oxime functional group at inert C(sp)-H bonds of ethers, amides, alcohols, amines, and alkanes via HAT with photoexcited eosin Y under mild conditions using air and a blue LED. Many useful functional groups are tolerated in this process, and the reaction is scalable. A series of mechanistic studies were carried out to support the radical pathway proposed for the process.

Photocatalytic Aerobic Coupling of Azaarenes and Alkanes via Nontraditional Cl Generation.

Herein, we demonstrate a nonconventional photocatalytic generation of Cl from a common chlorinated solvent, dichloroethane, under aerobic conditions and its successful utilization toward the cross-dehydrogenative coupling of alkanes and azaarenes via hydrogen atom transfer with Cl. The process is free from chloride salt, toxic oxidant, and UV light. It is applicable to a broad spectrum of substrates.

Heteroarylation of Ethers, Amides, and Alcohols with Light and O.

An efficient protocol for the C-H heteroarylation of ethers, amides, and alcohols using air and light under mild conditions is described. The reaction is applicable to a wide spectrum of functional groups. The generation of C-radicals via photoinduced aerobic oxidation of ethers, amides, and alcohols is the key feature of the process.

Hydrogen-Bonding Assisted Catalytic Kinetic Resolution of Acyclic β-Hydroxy Amides.

Enantioenriched acyclic α-substituted β-hydroxy amides are valuable compounds in chemical, material and medicinal sciences, but their enantioselective synthesis remains challenging. A catalytic kinetic resolution (KR) of such amides with selectivity factor(s) up to >200 is developed via enantioselective acylation of primary alcohol with N-heterocyclic carbene. An enhanced selectivity for the catalytic KR process is realized using cyclic tertiary amine as base additive.

A General Approach to Intermolecular Olefin Hydroacylation through Light-Induced HAT Initiation: An Efficient Synthesis of Long-Chain Aliphatic Ketones and Functionalized Fatty Acids.

Herein, an operationally simple, environmentally benign and effective method for intermolecular radical hydroacylation of unactivated substrates by employing photo-induced hydrogen atom transfer (HAT) initiation is described. The use of commercially available and inexpensive photoinitiators (Ph CO and NHPI) makes the process attractive. The olefin hydroacylation protocol applies to a wide array of substrates bearing numerous functional groups and many complex structural units.

Aerobic Acylarylation of α,β-Unsaturated Amides with Aldehydes.

Herein, we illustrate that molecular oxygen (O) is capable of promoting oxidative radical acylarylation of olefins with aliphatic aldehydes to afford acylated oxindoles in good yield (up to 97%). The key aspect of the process is the utilization of aldehyde auto-oxidation in developing aerobic radical olefin acylarylation. Kinetic studies confirm a lag phase for the reaction.

Palladium-Catalyzed Decarboxylative ortho-C(sp )-H Aroylation of N-Sulfoximine Benzamides at Room Temperature.

A palladium-catalyzed method for the decarboxylative ortho C-H acylation of N-sulfoximine benzamides is developed at room temperature. The catalytic method enables easy access to various functionalized 2-aroylaromatic carboxylic acid derivatives in good isolated yields. Based on our mechanistic studies, a Pd(II)/Pd(IV) catalytic cycle that involves aroyl radical intermediate is proposed for the reaction.

Enantioselective α-Amination of Acyclic 1,3-Dicarbonyls Catalyzed by N-Heterocyclic Carbene.

Herein, we describe a method for the catalytic enantioselective α-amination of α-substituted acyclic 1,3-ketoamides and 1,3-amidoesters that affords the products possessing N-substituted quaternary stereocenters with a chiral N-heterocyclic carbene (NHC). The reaction is based on the utilization of an intrinsic Brønsted base characteristic of NHC that enables the catalytic formation of a chiral ion pair comprising the enolate and the azolium ion. A series of challenging open-chain α-substituted 1,3-dicarbonyls are aminated via this method with ee's of ≤99%.

Synthesis of Phenolic Compounds via Palladium Catalyzed C-H Functionalization of Arenes.

Phenol and its derivatives are extremely useful compounds in organic synthesis, medicinal chemistry and material sciences. The synthesis of phenols involving selective construction of the C-O bond at a C-H bond of arenes using transition-metal catalysis represents the most appealing strategy. Indeed, active research is currently going on for the synthesis of valuable phenolic compounds using a transition-metal-catalyzed C-H functionalization strategy.

Radical C-H Acylation of Nitrogen Heterocycles Induced by an Aerobic Oxidation of Aldehydes.

An aerobic radical approach for the synthesis of unsymmetrical heteroaryl ketones is described herein. The reaction involves cross-dehydrogenative coupling between aldehydes and heteroaromatic bases with molecular oxygen (O ). The key aspect of the method is the generation of reactive acyl radical via homolytic activation of aldehyde C-H bond using O as the sole oxidant.

Highly Enantioselective Synthesis of Functionalized Glutarimide Using Oxidative N-Heterocyclic Carbene Catalysis: A Formal Synthesis of (-)-Paroxetine.

A simple yet highly effective approach toward enantioselective synthesis of trans-3,4-disubstituted glutarimides from readily available starting materials is developed using oxidative N-heterocyclic carbene catalysis. The catalytic reaction involves a formal [3 + 3] annulation between enals and substituted malonamides enabling the production of glutarimide derivatives in a single chemical operation via concomitant formation of C-C and C-N bonds. The reaction offers easy access to a broad range of functionalized glutarimides with excellent enantioselectivity and good yield.

N-Heterocyclic carbenes as chiral Brønsted base catalysts: a highly diastereo- and enantioselective 1,6-addition reaction.

Highly diastereo- and enantioselective 1,6-addition of 1,3-ketoamides to -quinone methides (-QMs) using chiral NHCs as Brønsted base catalysts is developed. The reaction is based on the utilization of a 1,3-ketoamide having acidic N-H that forms a chiral ion-pair consisting of the enolate and the azolium ion. Different β-ketoamides and functionalized -QMs are applicable to the reaction.

Molecular Oxygen Mediated Radical Dicarbofunctionalization of Olefin with Aldehyde.

Herein we present a metal- and peroxide-free method for the synthesis of sterically hindered amides bearing an all-carbon quaternary stereogenic center at the α-position via a one-pot alkylation/aryl-migration/desulfonylation radical cascade. The novel process is developed employing readily available and inexpensive aldehyde as an alkyl radical precursor and O as the sole oxidant. The method features a broad substrate scope, operational simplicity, convenient reagents, and scalability.

Asymmetric counteranion-directed Lewis acid organocatalysis for the scalable cyanosilylation of aldehydes.

Due to the high versatility of chiral cyanohydrins, the catalytic asymmetric cyanation reaction of carbonyl compounds has attracted widespread interest. However, efficient protocols that function at a preparative scale with low catalyst loading are still rare. Here, asymmetric counteranion-directed Lewis acid organocatalysis proves to be remarkably successful in addressing this problem and enabled a molar-scale cyanosilylation in quantitative yield and with excellent enantioselectivity.

Aerobic Radical-Cascade Alkylation/Cyclization of α,β-Unsaturated Amides: an Efficient Approach to Quaternary Oxindoles.

An efficient method for the aerobic radical-cascade alkylation/cyclization of α,β-unsaturated amides to afford functionalized oxindoles with a C3 quaternary stereocenter is described. The process is based on the generation of valuable alkyl radicals through sustainable aerobic C-H activation of aldehydes followed by decarbonylation using O2 as the sole oxidant. This method features a broad substrate scope, inexpensive alkyl radical precursors, and convenient reagents.

Dioxygen-Mediated Decarbonylative C-H Alkylation of Heteroaromatic Bases with Aldehydes.

An operationally simple and economical method for the direct alkylation of heteroaromatic bases employing readily available aldehydes as alkyl radical precursors and molecular oxygen as a reagent is presented. This simple transformation demonstrates a broad substrate scope with respect to aldehydes and nitrogen heterocycles, enabling the introduction of several medicinally important yet challenging alkyl moieties, such as ethyl, isopropyl, tert-butyl, and cyclohexyl to the different classes of heterocyclic bases in good to excellent yields.

The catalytic asymmetric Abramov reaction.

The first catalytic enantioselective Abramov reaction is described. The process is based on the utilization of a chiral disulfonimide catalyst, which efficiently avoids the difficulties encountered with metal-based catalysts. Several functionalized α-hydroxy phosphonates were synthesized in good yields and with excellent enantiomeric ratios of up to >99:1.