Palladium‐Catalyzed Decarboxylative sp‐sp2 Cross‐Coupling Reactions of Aryl and Vinyl Halides and Triflates with α,β‐Ynoic Acids using Silver Oxide

Palladium‐catalyzed decarboxylative sp‐sp² cross‐coupling reactions of aryl and vinyl halides and triflates with α,β‐ynoic acids using silver oxide have been developed. A variety of α,β‐ynoic acids were readily decarboxylated in the presence of silver oxide and then, generated in situ, silver acetylides were coupled with electrophiles in the presence of a palladium(0) catalyst under neutral conditions, producing either symmetrical or unsymmetrical diarylacetylenes, arylalkylacetylenes and arylvinylacetylenes in good to excellent yields.     

β‐Aryl Nitrile Construction via Palladium‐Catalyzed Decarboxylative Benzylation of α‐Cyano Aliphatic Carboxylate Salts

The palladium‐catalyzed decarboxylative benzylation of α‐cyano aliphatic carboxylate salts with benzyl electrophiles was discovered. This reaction exhibits good functional group compatibility and proceeds under relatively mild conditions. A diverse range of quaternary, tertiary and secondary β‐aryl nitriles can be conveniently prepared by this method.     

Room Temperature Palladium‐Catalyzed Decarboxylative Acyl/Aroylation using [Fe(III)(EDTA)(η2‐O2)]3− as Oxidant at Biological pH

The purple‐coloured iron peroxo complex [Fe(III)EDTA(η²‐O₂)]³⁻ as a novel reagent system for Pd‐catalyzed decarboxylative ortho‐acylation of acetanilides with α‐oxocarboxylic acids at room temperature in aqueous media has been realized. This reaction provides an effective access to ortho‐acylacetanilides under mild conditions.     

Intramolecular Photochemical Cross‐Coupling Reactions of 3‐Acyl‐2‐haloindoles and 2‐Chloropyrrole‐3‐carbaldehydes with Substituted Benzenes

Highly efficient syntheses of indolo[2,1‐a]isoquinolines, indolo[2,1‐a][2]benzazepines, pyrrolo[2,1‐a]isoquinolines and pyrrolo[1,2‐a]benzazepines in excellent yields have been achieved by the intramolecular photochemical cross‐coupling reactions of 3‐acyl‐2‐halo‐N‐(ω‐arylalkyl)indoles and 2‐chloro‐N‐(ω‐arylalkyl)pyrrole‐3‐carbaldehydes in acetone. A new heterocyclic ring system – pyrrolo[1,2‐d][1,4]benzoxazepine – has also been constructed for the first time in this work by the photocyclization of 2‐chloro‐N‐(2‐phenoxyethyl)pyrrole‐3‐carbaldehyde.     

Palladium‐Catalyzed Efficient and One‐Pot Synthesis of Diarylacetylenes from the Reaction of Aryl Chlorides with 2‐Methyl‐3‐butyn‐2‐ol

An efficient and practical synthetic method has been developed for the preparation of symmetrical diarylacetylenes from the direct reaction of aryl chlorides with 2‐methyl‐3‐butyn‐2‐ol catalyzed by palladium(II) chloride‐bis(tricyclohexylphosphine) [PdCl₂(PCy₃)₂] under mild reaction conditions. Unsymmetrical diarylated acetylenes could be also obtained by using two different aryl chlorides simultaneously. The catalytic procedure includes a novel one‐pot palladium‐catalyzed, double Sonogashira coupling of inactivated aryl chlorides without use of copper(I) as co‐catalyst.     

Direct Decarboxylative Alkynylation of α,α‐Difluoroarylacetic Acids under Transition Metal‐Free Conditions

An efficient and generally applicable protocol for decarboxylative coupling of α,α‐difluoroarylacetic acids with ethynylbenziodoxolone (EBX) reagents has been developed, affording α,α‐difluoromethylated alkynes bearing various functional groups in moderate to excellent yields. Remarkably, this potassium persulfate (K₂S₂O₈)‐promoted reaction employs water as solvent under transition metal‐free conditions, thus providing a green synthetic approach to α,α‐difluoromethylated alkynes.

     

Gold(I)‐Catalyzed Decarboxylation of Propargyl Carbonates: Reactivity Reversal of the Gold Catalyst from π‐Lewis Acidity to σ‐Lewis Acidity

A cationic gold(I)‐catalyzed decarboxylative etherification of propargyl carbonates to selectively produce propargyl ethers is reported. In the reaction the gold(I) catalyst shows a distinct σ‐Lewis acidity rather than the commonly observed π‐Lewis acidity, and thus catalyzes the decarboxylation of a variety of propargyl carbonates to give the corresponding propargyl ethers with high selectivity. This reaction represents a rare example of the tunable reactivity of cationic gold(I) complexes between σ‐Lewis acidity and π‐Lewis acidity.

     

Palladium‐Catalyzed One‐Pot Sonogashira Coupling,exo‐dig Cyclization and Hydride Transfer Reaction: Synthesis of Pyridine‐Substituted Pyrroles

An efficient palladium(II)‐catalyzed method for the synthesis of alkylated pyridine‐substituted pyrroles has been developed by a one‐pot three component reaction of β‐bromovinyl aldehydes, primary amines and 2‐alkynylpyridines in good yields. The reactions can also provide an efficient route to 2‐picolinoylpyrroles by slightly altering the reaction conditions.

     

Phosphine‐Free Palladium‐Catalyzed Decarboxylative Coupling of Alkynylcarboxylic Acids with Aryl and Heteroaryl Halides

We herein report the design and development of a carboxyamido/carbene ligand and its Pd‐complex for the decarboxylative coupling of alkynylcarboxylic acids with aryl and heteroaryl halides to afford arylalkynes.     

The One‐Pot Wittig Reaction: A Facile Synthesis of α,β‐Unsaturated Esters and Nitriles by Using Nanocrystalline Magnesium Oxide

Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions.     

Synthesis of 1,4‐Diarylbuta‐1,3‐dienes through Palladium‐ Catalyzed Decarboxylative Coupling of Unsaturated Carboxylic Acids

It has been found that readily available hydroxylated cinnamic acids such as ferulic acid undergo palladium‐catalyzed decarboxylative coupling with aryl iodides and internal alkynes in a 1:1:1 manner to produce 1,4‐diarylbuta‐1,3‐dienes. The butadiene synthesis has also been achieved through the coupling of aryl halides with dienoic acids. Some of the products exhibit solid‐state fluorescence.     

A Mild Palladium‐Catalyzed Suzuki Coupling Reaction of Quinoline Carboxylates with Boronic Acids

A palladium‐catalyzed cross‐coupling between aryl carboxylates and boronic acids has been achieved for the first time by taking advantage of the enhanced reactivity of quinoline 4‐carboxylates. Also for the first time a Suzuki coupling reaction via a self‐activation of boronic acids without addition of base is described. The reactions proceed under mild conditions (25–65 °C) to give excellent yields, and a wide range of functionalities is tolerated.     

Palladium‐Catalyzed Decarboxylative Acylation of O‐Phenyl Carbamates with α‐Oxocarboxylic Acids at Room Temperature

A palladium‐catalyzed oxidative acylation of O‐phenyl carbamates with α‐oxocarboxylic acids via selective aromatic C H bond activation is described. This protocol represents the first ortho‐acylation of phenol derivatives, and a catalytic amount of triflic acid additive is crucial for this transformation.     

Ruthenium(II)‐Catalyzed Protocol for Preparation of Diverse α,β‐ and β,β‐Dihaloenones from Diazodicarbonyls

Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.

     

A New One‐Pot Synthesis of Polysubstituted Indoles from Pyrroles and β‐Nitroacrylates

The reaction of β‐nitroacrylates with pyrroles, under solvent‐ and catalyst‐free conditions, allows the formation of Friedel–Crafts adducts which, after in situ treatment with Amberlyst 15 in isopropyl alcohol under reflux, provide polysubstituted indoles, via a benzannulation reaction, in a one‐pot process.     

Rhodium‐Catalyzed Asymmetric Hydroformylation of 1,1‐Disubstituted Allylphthalimides: A Catalytic Route to β3‐Amino Acids

The high enantioselective rhodium‐catalyzed hydroformylation of 1,1‐disubstituted allylphthalimides has been developed. By employing chiral ligand 1,2‐bis[(2S,5S)‐2,5‐diphenylphospholano]ethane [(S,S)‐Ph‐BPE], a series of β³‐aminoaldehydes can be prepared with up to 95% enantioselectivity. This asymmetric procedure provides an efficient alternative route to prepare chiral β³‐amino acids and alcohols.     

Stereoselective Palladium‐Catalyzed Alkenylation and Alkynylation of Thioglycosides

An efficient and unprecedented palladium‐catalyzed S‐glycosylation reaction of a range of alkenyl and alkynyl halides by using thiosugars as nucleophile partners has been established. With palladium diacetate in combination with Xantphos as the catalytic system, a variety of β‐alkenylthioglycosides as well as β‐alkynylthioglycosides can be prepared in good to excellent yields. The efficiency of this general protocol was well‐demonstrated by the formal synthesis of a leaf‐closure β‐glucosidase inhibitor.

     

Palladium‐Catalyzed Two‐Component Domino Coupling Reaction of (Z)‐β‐Bromostyrenes with Norbornenes: Synthesis of 1,5‐Enynes

Polyfunctional molecules, 1,5‐enynes, have been achieved via a palladium(0)‐catalyzed domino coupling reaction of (Z)‐β‐bromostyrenes with norbornenes in the presence of cesium carbonate and N,N‐dimethylformamide. The process involves a double Heck‐type procedure, two‐fold C(sp²) H activation and formation of two carbon‐carbon bonds. There are possibilities of diversified transformation for the domino coupling of (Z)‐β‐bromostyrenes with norbornenes, the procedure is successfully driven to 1,5‐enynes via accurate adjustment of the reaction conditions.

     

Synthesis of 2H‐Indazoles via Tandem Palladium‐Catalyzed Deacylative Cross‐Coupling and Denitrogenative Cyclization of 2‐Iodoazoarenes and 2‐Iodoaryltriazenes with Acyldiazoacetates in One‐Pot

A synthetic method to prepare a wide range of 2H‐indazoles was developed via a tandem palladium‐catalyzed deacylative cross‐coupling reaction of 2‐iodoazoarenes and 2‐iodoaryltriazenes with acyldiazoacetates and denitrogenative cyclization reaction of in situ generated diazoacetates having azoaryl and triazenylaryl moieties in one‐pot. Additionally, azoaryl‐substituted diazoacetates underwent palladium‐catalyzed denitrogenative cyclization to produce 2H‐indazoles. The present reaction is a good example in which a Pd(0)‐catalyst is involved in two catalytic cycles in one‐pot.

     

Ruthenium‐Catalyzed Oxidation of the Porphyrin β,β′‐Pyrrolic Ring: A General and Efficient Approach to Porpholactones

We describe an efficient ruthenium‐catalyzed oxidation of the β,β′‐pyrrolic ring on the porphyrin periphery. Through the conversion of a β,β′‐double bond to a lactone moiety, the direct preparation of porpholactones from porphyrins is achieved, which previously suffered from needing toxic reagents, multiple synthetic steps and low yields. The generality of this method has been investigated with various porphyrins with different electronic and steric effects, even some metalloporphyrins, and so represents a general and efficient approach for the synthesis of the intriguing porpholactone derivatives.