1‐(α‐Aminobenzyl)‐2‐naphthol as phosphine‐free ligand for Pd‐catalyzed Suzuki and one‐pot Wittig‐Suzuki reaction

Air stable and easily accessible, 1‐(α‐aminobenzyl)‐2‐naphthols are used as efficient phosphine‐free ligands in palladium‐catalyzed Suzuki reaction for a variety of substrates under conventional heating as well as ultrasonic conditions. Multi‐brominated aromatic substrates were successfully converted to corresponding arylated moieties with good conversion and selectivity. A novel one‐pot two‐step cascade reaction strategy involving Wittig and Suzuki reactions is developed for efficient synthesis of 4‐styryl biphenyls (C₆‐C₂‐C₆‐C₆ unit). Copyright © 2012 John Wiley & Sons, Ltd.     

Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine

A new, convenient and efficient AgNO₃‐catalyzed strategy for the preparation of 2‐(benzo[d]azol‐2‐yl)phenol derivatives in good to excellent yields (63–98%) is described. The reaction proceeds via condensation/intramolecular nucleophilic addition/oxidation process between substituted salicylaldehydes and 2‐aminothiophenol, 2‐aminophenol or benzene‐1,2‐diamine under mild reaction conditions. Notably, this reaction utilizes cheap AgNO₃ as a readily available and low‐cost benign oxidant at low catalyst loadings with excellent functional group tolerance.     

Palladium‐catalyzed Heck coupling of 2‐vinylpyridine with aryl chlorides

An efficient PdCl₂(PCy₃)₂‐catalyzed cross‐coupling reaction of 2‐vinylpyridine with aryl chlorides to afford trans ‐2‐styrylpyridines with a variety of functional groups on the benzene ring is described. Copyright © 2008 John Wiley & Sons, Ltd.     

First report of a nano‐Cu2O‐catalyzed protocol for homo‐coupling reaction of terminal alkynes in water/ionic liquid medium

A new, efficient and green protocol for the nano‐Cu₂O‐catalyzed homo‐coupling reaction of terminal alkynes has been developed, using water/ionic liquid as an environmentally friendly solvent. Moreover, the system also allows the synthesis of unsymmetric 1,3‐diynes by cross‐coupling of two different terminal alkynes. It is noteworthy that the nano‐Cu₂O‐catalyzed methodology is a good supplement to copper catalyst for the Glaser‐type homo‐coupling reaction. Copyright © 2016 John Wiley & Sons, Ltd.     

Assembly of homoallylamine derivatives through iron‐catalyzed three‐component sulfonamidoallylation reaction

An efficient FeCl₃‐catalyzed three‐component reaction between aldehydes, sulfonamides and allylsilanes has been achieved, which provides a convenient, atom‐economic and green way to construct homoallylamine derivatives. In addition, this reaction exhibits excellent syn stereoselectivity with γ‐substituted allylsilanes.     

Copper(II)‐Catalyzed Tandem Synthesis of Substituted 3‐Methyleneisoindolin‐1‐ones

An efficient strategy for the synthesis of a variety of 3‐methyleneisoindolin‐1‐ones has been developed. The reaction proceeded from coupling of 2‐iodobenzamides (or 2‐bromobenzamides) and terminal alkynes via Cu(OAc)₂·H₂O/2,2′‐biimidazole catalyzed in DMF at 60°C and subsequent additive cyclization produced substituted 3‐methyleneisoindolin‐1‐ones in good to excellent yields.     

Enantioselective Nitroso‐Diels–Alder Reaction and Its Application for the Synthesis of (−)‐Peracetylated Conduramine A‐1

Cu^I‐catalyzed enantioselective nitroso‐Diels–Alder reactions (NDA reactions) of 2‐nitrosopyridine with various dienes are presented. The [CuPF₆(MeCN)₄]/Walphos‐CF₃ catalyst system is best suited to catalyze the NDA reaction of various dienes by using 2‐nitrosopyridine as a dienophile. In most of the cases studied, cycloadducts are obtained in quantitative yield with very good to excellent enantioselectivities. Based on DFT calculations, a model to explain the stereochemical outcome of the NDA reaction is presented. Finally, an efficient short synthesis of (?)‐peracetylated conduramine A‐1 by applying the enantioselective NDA reaction as a key step is described.     

Palladium‐Catalyzed Multi‐Component Reactions of N‐Tosylhydrazones, 2‐Iodoanilines and CO2 towards 4‐Aryl‐2‐Quinolinones

A palladium‐catalyzed three‐component reaction between N‐tosylhydrazones, 2‐iodoanilines and atmospheric pressure CO₂ was developed whereby a tandem carbene migration insertion/lactamization strategy afforded 4‐aryl‐2‐quinolinones in moderate to good yields. Notably, a wide range of functional groups were tolerated in this procedure. This protocol features the simultaneous formation of four novel bonds; two C?C, one C=C and one C?N (amide), representing an efficient methodology for incorporation of CO₂ into heterocycles.     

Yb(OTf)3: An Efficient Catalyst for the Synthesis of 11‐Aryl‐7H‐cyclopenta[b][4,7]phenanthrolin‐10(11H)‐One Derivatives

A mild and efficient method for the synthesis of 8,9‐dihydro‐11‐aryl‐7H‐cyclopenta[b][4,7]phenanthrolin‐10(11H)‐one derivatives via three‐component reaction of aromatic aldehyde, quinolin‐6‐amine and cyclopentane‐1,3‐dione is described catalyzed by Yb(OTf)₃. The features of this procedure are mild reaction conditions, good to high yields, and operational simplicity.     

Lewis Acid Catalyzed Synthesis of 1‐Aryl‐1,2‐dihydro‐naphtho[1,2‐e][1,3]oxazin‐3‐ones under Solvent Free Conditions: A Mechanistic Approach

Lewis acids catalyzed highly efficient one‐pot three component coupling of β‐naphthol, benzaldehydes and urea to produce 1‐aryl‐1,2‐dihydro‐naphtho[1,2‐e][1,3]oxazin‐3‐one derivatives under solvent free conditions is described. Mechanistic studies confirmed that product formation is possible only at very high temperature (140–150°C) and at lower temperature (90–100°C) formation of 14‐aryl‐14H‐dibenzo(a,j)xanthenes was observed. Among the nine Lewis acids screened, iodine, P₂O₅ and Yb(OTf)₃ are found to be most effective catalyst for this multicomponent reaction.     

Synthesis of substituted quinolines via B(C6F5)3‐catalyzed aniline‐aldehyde‐pyruvate oxidative annulation

A metal‐free method to construct quinoline derivatives via B(C₆F₅)₃‐catalyzed cyclization of anilines with aldehyde derivatives and pyruvates is described. This three‐component cascade reaction provides an efficient approach for the easy access to various substituted quinoline‐4‐carboxylic esters with 71% to 92% yield. The utility of this methodology was further demonstrated by gram‐scale formal synthesis of the antimalarial drug DDD107498.     

Microwave‐Accelerated Pd‐Catalyzed Desulfitative Direct C2‐Arylation of Free (NH)‐Indoles with Arylsulfinic Acids

The rapid and efficient direct C2‐arylation of free (NH)‐indoles with arylsulfinic acids proceeded through a microwave‐accelerated palladium‐catalyzed desulfitation reaction. By using PdCl₂ as a catalyst, silver acetate as an oxidant, and H₂SO₄ as an additive, arylsulfinic acids with both electron‐donating and electron‐withdrawing groups underwent desulfitative coupling with an array of free (NH)‐indoles, thereby selectively providing C2‐arylindoles in good yields.     

Silver‐Catalyzed Formal Insertion of Arynes into RfI Bonds

An unprecedented silver‐catalyzed formal insertion of arynes into R_f?I (R_f=CF₃, C₂F₅) bonds has been developed. This protocol provides easy access to various ortho‐perfluoroalkyl iodoarenes under mild conditions. In this insertion reaction, an ionic atom‐transfer reaction of R_fI occurs, and a silver‐mediated metathesis process is involved in the efficient transfer of the electropositive iodine atom.     

Benzylamine as Hydrogen Transfer Agent: Cobalt‐Catalyzed Chemoselective C=C Bond Reduction of β‐Trifluoromethylated α,β‐Unsaturated Ketones via 1,5‐Hydrogen Transfer

An efficient cobalt‐catalyzed chemoselective reduction of β‐CF₃‐α,β‐unsaturated ketones using benzylamine as hydrogen transfer agent involving intramolecular 1,5‐hydrogen transfer is reported. The reaction proceeded smoothly with a relatively wide range of substrates including those bearing aromatic heterocycles such as a furyl ring system in high yields (74–92 %). This provides an efficient method for the synthesis of β‐CF₃ saturated ketones in one‐pot. This methodology was also applied to the selective C=C reduction of other enone substrates bearing no β‐CF₃‐substituent, of which β‐substituted or β,β‐disubstituted enones are tolerated, giving the desired products in good yields (72–75 %). Mechanistic studies indicate that the reaction involves 1,5‐hydrogen transfer.     

Pd‐catalyzed Desulfitative reaction of Aryltrifluoroborates with sodium Arenesulfinates in water

An efficient procedure for the synthesis of biaryls was catalyzed by Pd(CH₃CN)₄(BF₄)₂ is reported. This Pd‐catalyzed cross‐coupling reaction of aryltrifluoroborates with sodium arenesulfinates was developed under mild and environmentally benign conditions, in water without any ligand or additive. The reaction gave a range of structurally diverse unsymmetrical bi‐aryl molecules with excellent yields, in which the byproduct was sulfur dioxide. It is worth noting that this protocol is also applicable to many heterocyclic aromatics such as thiophene, furan, pyridine, quinoline, isoquinoline and indole.     

First Total Synthesis of 9‐Hydroxy‐8H‐pyrano[3,2‐f]indol‐2‐one

A simple and efficient approach to synthesize a novel pyrrolocoumarin 9‐hydroxy‐8H‐pyrano[3,2‐f]indol‐2‐one ( 7 ) has been described. Starting from vanillin, the key intermediate 7‐methoxy‐1H‐indol‐6‐yl propiolate ( 6 ) was synthesized in six steps. Then, the target compound was obtained by forming pyrone‐ring and demethylation simultaneously in one step. A plausible mechanism invoking PtCl₄ catalyzed one‐step reaction of cyclization and demethylation was also presented.     

Catalytic Enantioselective Cyclopropenation of Internal Alkynes: Access to Difluoromethylated Three‐Membered Carbocycles

Herein we described an efficient Rh^II‐catalyzed enantioselective cyclopropenation reaction of internal alkynes with a masked difluorodiazoethane reagent (PhSO₂CF₂CHN₂, Ps‐DFA). This asymmetric transformation offers efficient access to a broad range of enantioenriched difluoromethylated cyclopropenes (40 examples, up to 99 % yield, 97 % ee). The synthetic utility of obtained strained carbocycles is demonstrated by subsequent stereodefined processes, including cross‐couplings, hydrogenation, Diels–Alder reaction, and Pauson–Khand reaction.     

Silver salts and DBU cooperatively catalyzed domino reaction of propargylic alcohols with trifluoromethyl ketones: direct method to trifluoromethyl‐substituted 5‐alkylidene‐1,3‐dioxolane derivatives

A general and efficient synthesis of trifluoromethyl‐substituted 5‐alkylidene‐1,3‐dioxolanes using AgNO₃ and DBU cooperatively catalyzed domino reaction of propargylic alcohols and trifluoromethyl ketones is described. The reaction tolerates a broad range of functional groups, and the desired products are obtained in good to excellent yields (62–99%) with acceptable diastereoselectivities. Copyright © 2016 John Wiley & Sons, Ltd.     

NaY Zeolite Functionalized by Sulfamic Acid/Cu(OAc)2 as a Novel and Reusable Heterogeneous Hybrid Catalyst in Efficient Synthesis of Bis,Tris, and Tetrakis(indolyl)methanes, 3,4‐Dihydropyrimidin‐2(1H)‐ones,and 2‐Aryl‐1H‐benzothiazoles

An efficient acid‐catalyzed synthesis of some bis, tris, and tetrakis(indolyl)methanes, 3,4‐dihydropyrimidin‐2(1H )‐ones, and 2‐aryl‐1H ‐benzothiazoles is reported using NaY zeolite functionalized by sulfamic acid/Cu(OAc )₂ (NaY zeolite‐NHSO₃H /Cu(OAc )₂) in excellent yield. The heterogeneous catalyst has a simple work‐up procedure and could be recycled and reused for six reaction cycles.     

One‐pot synthesis of polyfluoroterphenyls via palladium‐catalyzed Suzuki–Miyaura coupling of chlorobromobenzene and CH bond functionalization of perfluoroarenes

An efficient tandem route for the synthesis of polyfluoroterphenyl derivatives has been developed. The target compounds were obtained in moderate to good yields by a Pd(OAc)₂‐catalyzed three‐component coupling reaction involving palladium‐catalyzed direct C? H activation of perfluoroarenes. This in turn will set the stage for a wide application of this useful reaction for the synthesis of fluorinated liquid crystal compounds containing the privileged polyfluoroterphenyl structure. Copyright © 2014 John Wiley & Sons, Ltd.