Construction of -Aryl-Substituted Pyrrolidines by Successive Reductive Amination of Diketones via Transfer Hydrogenation.

-aryl-substituted pyrrolidines are important moieties widely found in bioactive substances and drugs. Herein, we present a practical reductive amination of diketones with anilines for the synthesis of -aryl-substituted pyrrolidines in good to excellent yields. In this process, the -aryl-substituted pyrrolidines were furnished via successive reductive amination of diketones via iridium-catalyzed transfer hydrogenation.

Iridium-catalysed reductive allylic amination of α,β-unsaturated aldehydes.

Allylic amination is a powerful tool for constructing -allylic amines widely found in bioactive molecules. Generally, allylic alcohols and unsaturated hydrocarbons have been considered for allylic amination reactions to minimize waste production. Herein, we present an iridium-catalysed method for reductive allylic amination of α,β-unsaturated aldehydes with amines to afford -allylic amines under air conditions.

One-pot reductive amination of carbonyl compounds and nitro compounds Ir-catalyzed transfer hydrogenation.

The formation of C-N bond is a vital synthetic tool for establishing molecular diversity, which is highly sought after in a wide range of biologically active natural products and drugs. Herein, we present a new strategy for the synthesis of secondary amines iridium-catalyzed one-pot reductive amination of carbonyl compounds with nitro compounds. This method is demonstrated for a variety of carbonyl compounds, including miscellaneous aldehydes and ketones, which are compatible with this catalytic system, and deliver the desired products in good yields under mild conditions.

Recent advances of Cp*Ir complexes for transfer hydrogenation: focus on formic acid/formate as hydrogen donors.

Transfer hydrogenation reactions offer synthetically powerful strategies to deliver various hydrogenated compounds with the advantages of efficiency, atom economy, and practicability. On one hand, formic acid/formate function as promising hydrogen sources owing to their readily obtainable, inexpensive, and easy to handle nature. On the other hand, Cp*Ir complexes show high activities in transfer hydrogenation.

Furan-2-yl Anions as γ-Oxo/Hydroxyl Acyl Anion Equivalents Enabled by Iridium-Catalyzed Chemoselective Reduction.

The last piece of the puzzle: Furan-2-yl anions are first demonstrated as robust γ-oxo and γ-hydroxyl acyl anion equivalents to convert aldehydes and ketones into trifunctionalized dihydroxyl ketones and hydroxyl diones through sequential nucleophilic addition, Achmatowicz rearrangement, and herein freshly established iridium-catalyzed highly selective transfer hydrogenation reduction.

Access to Saturated Oxygen Heterocycles and Lactones via Electrochemical Sulfonylative Oxycyclization of Alkenes with Sulfonyl Hydrazides.

A facile electrochemical sulfonylative cycloetherification of linear unsaturated alcohols with sulfonyl hydrazides under mild conditions has been accomplished. This catalyst- and oxidant-free protocol proceeds via electro-oxidation, followed by radical addition, as well as an intramolecular oxygen nucleophilic process. This methodology is compatible with a broad substrate scope and good functional group compatibility, which provides a valuable and convenient synthetic tool for the synthesis of saturated five-, six-, seven-, and eight-membered ring oxygen heterocycles.

Cyclometalated iridium complexes-catalyzed acceptorless dehydrogenative coupling reaction: construction of quinoline derivatives and evaluation of their antimicrobial activities.

The acceptorless dehydrogenative coupling (ADC) reaction is an efficient method for synthesizing quinoline and its derivatives. In this paper, various substituted quinolines were synthesized from 2-aminobenzyl alcohols and aryl/heteroaryl/alkyl secondary alcohols in one pot via a cyclometalated iridium-catalyzed ADC reaction. This method has some advantages, such as easy availability of raw materials, mild reaction conditions, wide range of substrates, and environmental friendliness which conforms to the principles of green chemistry.

Synthesis of -alkoxy amines and hydroxylamines the iridium-catalyzed transfer hydrogenation of oximes.

Cationic iridium (Ir) complexes were found to catalyze the transfer hydrogenation of oximes to access -alkoxy amines and hydroxylamines, and the reaction was accelerated by trifluoroacetic acid. The practical application of this protocol was demonstrated by a gram-scale transformation and two-step synthesis of the fungicide furmecyclox (BAS 389F) in overall yields of 92 and 85%, respectively. An asymmetric protocol using chiral Ir complexes to afford chiral -alkoxy amines was demonstrated, but the low yields/ee obtained indicated that further development was required.

Ru-Catalyzed Asymmetric Addition of Arylboronic Acids to Aliphatic Aldehydes via -Chiral Monophosphorous Ligands.

Chiral alcohols are among the most widely applied in fine chemicals, pharmaceuticals and agrochemicals. Herein, the Ru-monophosphine catalyst formed in situ was found to promote an enantioselective addition of aliphatic aldehydes with arylboronic acids, delivering the chiral alcohols in excellent yields and enantioselectivities and exhibiting a broad scope of aliphatic aldehydes and arylboronic acids. The enantioselectivities are highly dependent on the monophosphorous ligands.

Photoinduced radical cascade cyclization of acetylenic acid esters with oxime esters to access cyanalkylated coumarins.

A photoinduced radical cascade cyclization of acetylenic acid esters with oxime esters is described, providing cyanalkylated coumarins in superior yields under mild conditions. Radical capture and luminescence quenching experiments showed that this transformation was accomplished a radical addition/5- spirocyclization/1,2-ester migration process.

Selective Synthesis of Ketones and Chiral Allylic Alcohols from the Addition of Arylboronic Acids to α,β-Unsaturated Aldehydes Mediated by a Transition Metal/Monophosphorus Ligand System.

Here, we demonstrated a transition metal-mediated/monophosphorus ligand system for the selective synthesis of ketones or chiral allylic alcohols in high yields/enantiomeric excess from the 1,2-addition of arylboronic acids to α,β-unsaturated aldehydes. Notably, isomerization of the chiral allylic alcohols to ketones was suppressed by the Ru-catalyzed/monophosphorus ligand system. The asymmetric catalytic system provides an alternative and efficient method of preparing chiral allylic alcohols.

Iridium-catalyzed reductive etherification of α,β-unsaturated ketones and aldehydes with alcohols.

An iridium complex-catalyzed reductive etherification of α,β-unsaturated ketones and aldehydes with primary alcohols is presented, affording allyl ethers in excellent yields. Deuterated and control experiments showed that this etherification transformation proceeded through a cascade transfer hydrogenation and alcohol condensation process. Moreover, the utility of this protocol is evidenced by the gram-scale performance.

pH-Mediated Selective Synthesis of N-Allylic Alkylation or N-Alkylation Amines with Allylic Alcohols via an Iridium Catalyst in Water.

Amination of allylic alcohols is an effective approach in the facile synthesis of -allylic alkylation or -alkylation amines. Recently, a series of catalysts were devised to push forward this transformation. However, current synthetic methods are typically limited to achieve either -allylic alkylation or -alkylation products via a certain catalyst.

Substrate-Controlled Cu(OAc)-Catalyzed Stereoselective Semi-Reduction of Alkynes with MeOH as the Hydrogen Source.

A substrate-controlled stereoselective semi-reduction of alkynes with MeOH as the hydrogen source has been developed, and readily available Cu(OAc) (copper acetate) is utilized as an optimal catalyst. The detailed investigation of the mechanism revealed distinct catalytic processes for the ()- and ()-alkenes, respectively. As a result, a diversity of alkynes (including terminal, internal alkynes etc.

Iridium Complex-Catalyzed Transfer Hydrogenation of N-Heteroarenes and Tentative Asymmetric Synthesis.

An iridium-catalyzed transfer hydrogenation of N-heteroarenes to access a series of substituted 1,2,3,4-tetrahydroquinoline derivatives in excellent yields is disclosed. This transformation is distinguished with water-soluble and air-stable iridium complexes as the catalyst, formic acid as the hydrogen source, mild reaction conditions, and broad functional group compatibility. Most importantly, a tentative chiral ,-chelated Cp*Ir(III) complex-catalyzed enantioselective transfer hydrogenation is also presented, affording chiral products in excellent yields and good enantioselectivities.

Amide Iridium Complexes As Catalysts for Transfer Hydrogenation Reduction of -sulfonylimine.

Sulfonamide moieties widely exist in natural products, biologically active substance, and pharmaceuticals. Here, an efficient water-soluble amide iridium complexes-catalyzed transfer hydrogenation reduction of -sulfonylimine is developed, which can be carried out under environmentally friendly conditions, affording a series of sulfonamide compounds in excellent yields (96-98%). In comparison with organic solvents, water is shown to be critical for a high catalytic transfer hydrogenation reduction in which the catalyst loading can be as low as 0.

Cyclometalated Iridium Complex-Catalyzed -Alkylation of Amines with Alcohols via Borrowing Hydrogen in Aqueous Media.

This paper develops a methodology for cyclometalated iridium complex-catalyzed -alkylation of amines with alcohols via borrowing hydrogen in the aqueous phase. The cyclometalated iridium catalyst-mediated -alkylation of amines with alcohols displays high activity (S/C up to 10,000 and yield up to 96%) and ratio of amine/imine (up to >99:1) in a broad range of substrates (up to 46 examples) using water as the green and eco-friendly solvent. Most importantly, this transformation is simple, efficient, and can be performed at a gram scale, showcasing its potential for industrially synthesizing -alkylamine compounds.

Highly Catalytic Enantioselective Reformatsky Reaction with Aldehydes and Ketones Using an Available Prolinol Ligand.

A highly MeZn-mediated catalytic enantioselective Reformatsky reaction of aldehydes and ketones with ethyl iodoacetate using a readily available prolinol ligand is reported. This reaction provides an efficient method for the construction of β-hydroxy esters in up to 98% yield and 95% enantiomeric excess (ee) value. A wide range of functional groups are tolerated and the practicality of this protocol is demonstrated by performing the reaction on a gram scale.

Recent advances in the oxime-participating synthesis of isoxazolines.

Isoxazoline compounds are used as important intermediates for the synthesis of organic molecules, which are widely used in the chemical and life science industries. Oxime-participating cyclization has emerged as an efficient strategy for the construction of isoxazolines. This review is devoted to highlighting the main achievements (since 2010) in the development of methodologies for the synthesis of isoxazolines.

Photoredox-Catalyzed Oxy-/Aminofluoroalkylative Cyclization of Alkenes.

Here we describe a photoredox-catalyzed oxy-/aminofluoroalkylative cyclization of alkenes for coupling available -I reagents to generate fluoroalkylated 2,3-dihydrobenzofuran and indolin derivatives with good to excellent yields under mild conditions. A wide range of functional groups are tolerated. The mechanistic investigation of radical trapping and cyclic voltammetry experiments proposed that a radical/SET (single electron transfer) pathway proceeded in this reaction.

Silver(i)-catalyzed addition of pyridine-N-oxides to alkynes: a practical approach for N-alkenoxypyridinium salts.

A smooth catalytic approach to N-alkenoxypyridinium salts by using pyridine-N-oxides as the nucleophilic partner with alkynes under acidic conditions has been developed. This method uses different Ag(i) salts, with 5% AgOAc being the most efficient, to provide an efficient, practical and alternative way to obtain valuable N-alkenoxypyridinium salts with good to excellent yields (up to 93%).

Isoquinoline-1-Carboxylate as a Traceless Leaving Group for Chelation-Assisted Glycosylation under Mild and Neutral Reaction Conditions.

Glycosyl isoquinoline-1-carboxylate was developed as a novel benchtop stable and readily available glycosyl donor. The glycosylation reaction was promoted by the inexpensive Cu(OTf) salt under mild reaction conditions. The copper isoquinoline-1-carboxylate salt was precipitated from the solution and thus rendered a traceless leaving group.

Iridium-Catalyzed Asymmetric Ring-Opening of Oxabenzonorbornadienes with N-Substituted Piperazine Nucleophiles.

Iridium-catalyzed asymmetric ring-opening of oxabenzonorbornadienes with N-substituted piperazines was described. The reaction afforded the corresponding ring-opening products in high yields and moderate enantioselectivities in the presence of 2.5 mol % [Ir(COD)Cl]₂ and 5.

The asymmetric Cu(II)-indolinylmethanol complex catalyzed Diels-Alder reaction of 2-vinylindoles with β,γ-unsaturated α-ketoesters: an efficient route to functionalized tetrahydrocarbazoles.

An efficient asymmetric Diels-Alder reaction of 2-vinylindoles with β,γ-unsaturated α-ketoesters has been developed for the construction of functionalized tetrahydrocarbazoles. The products were obtained in high yields (up to 96%) with good stereoselectivities (ee up to 95%, dr up to >99 : 1).

Asymmetric ring-opening of oxabenzonorbornadiene with amines promoted by a chiral iridium-monophosphine catalyst.

A new iridium-monophosphine catalyst is found to be efficient for asymmetric ring-opening of benzonorbornadiene with amines, providing a series of chiral substituted dihydronaphthalenes in high yields (up to 98%) and excellent enantioselectivities (>99%).