Carbonylative Annulation Research Articles

Construction of palladium complex supported on magnetic nanoparticles as an efficient recoverable nanocatalyst for synthesis of flavones through carbonylative annulation

Construction of palladium complex supported on magnetic nanoparticles as an efficient recoverable nanocatalyst for synthesis of flavones through carbonylative annulation

Silver trifluoroacetate as a bifunctional reagent for palladium-catalyzed oxidative carbonylative [4 + 1] annulation of aromatic acids

AgTFA is disclosed as a bifunctional reagent, i.e. unprecedented in-situ CO source and oxidant in oxidative carbonylative annulation. The simple operation enables silver to be recovered easily and make AgTFA superior to other transition-metal carbonyl agents.

Recyclable Palladium-Catalyzed Carbonylative Coupling of 2-Iodoanilines, Trimethyl Orthoformate, and Amines: A Practical Synthesis of Quinazolin-4(3H)-ones

AbstractAn efficient heterogeneous palladium-catalyzed carbonylative annulation of 2-iodoanilines, trimethyl orthoformate, and amines has been developed. The reaction proceeds smoothly in toluene at 110 °C using N,N-diisopropylethylamine (DiPEA) as base and 2 mol% of MCM-41-anchored bidentate phosphine palladium complex [MCM-41-2P-Pd(OAc)2] as catalyst under 10 bar of carbon monoxide and provides a general and practical method for the construction of a wide variety of quinazolin-4(3H)-ones in good to excellent yields from commercially easily available starting materials. This heterogenized palladium catalyst can be easily recovered via a simple centrifugation process and reused more than nine times with almost consistent catalytic efficiency.

Recyclable palladium-catalyzed carbonylative annulation of 2-iodoanilines with acid anhydrides: A practical synthesis of 2-alkylbenzoxazinones

A highly efficient heterogeneous palladium-catalyzed carbonylative annulation of 2-iodoanilines and acid anhydrides has been developed. The reaction proceeds effectively in toluene using N,N-diisopropylethylamine (DiPEA) as the base at 100 °C under 2 bar of CO and provides a novel, general, and practical method for the assembly of a wide variety of 2-alkylbenzoxazinones with high functional group tolerance and good to excellent yields. This supported palladium complex can be readily separated from the product and recovered by a simple filtration of the reaction solution and reused up to seven times with almost consistent catalytic efficiency.

Metal-Free C-H [5 + 1] Carbonylation of 2-Alkenyl/Pyrrolylanilines Using Dioxazolones as Carbonylating Reagents.

A novel metal-free C-H [5 + 1] carbonylative annulation of 2-alkenyl/pyrrolylanilines with dioxazolones has been established for the assembly of the privileged quinolinones and pyrrolyl-fused quinoxalinones. Entirely differing from the existing reports, the dioxazolones herein behave with an innovative chemistry and first emerge as carbonylating reagents to participate in annulation reactions. Moreover, this process features exceedingly simple operation (only solvent) and tolerates both vinyl and aryl substrates. Comprehensive mechanistic studies indicate that the formed isocyanate intermediate plays a crucial role in enabling the carbonylation annulation.

The Trityl Cation Embedded into a [7]Helicene-Like Backbone: Preparation and Application as a Lewis Acid Catalyst

AbstractThe synthesis of a helically chiral carbenium ion is reported. The new motif is essentially a trityl cation embedded into a [7]helicene-like framework. The key step in its preparation establishes the π-extended fluorenone system in one step by an unprecedented palladium-catalyzed carbonylative annulation of a 4,4′-biphenanthryl-3,3′-diyl precursor. The racemic form of the new carbon Lewis acid was found to catalyze a representative set of reactions typically promoted by the trityl cation.

Palladium-catalyzed cascade carbonylative annulation between alkene-tethered aryl iodides and carbon monoxide.

Rapid construction of molecules bearing all-substituted quaternary stereocenters represents a highly significant but challenging task in organic synthesis. Herein, we report a novel palladium-catalyzed cascade between alkene-tethered aryl iodides and carbon monoxide, which has resulted in a practical and powerful method for the synthesis of complex polycyclic molecules containing aryl-substituted quaternary stereocenters. Mechanistic studies suggested that the reaction proceeded via a Heck-type carbonylative cyclization, followed by a ketene-involved Friedel-Crafts acylation.

Palladium-Catalyzed Carbonylative Annulation of 1-Hydroxy-o-Carborane and Internal Alkynes via Regioselective B-H Activation.

A Pd-catalyzed three-component carbonylative-annulation of 1-hydroxy-o-carborane, internal alkyne and carbon monoxide has been achieved via direct and regioselective cage B-H activation. A class of C,B-substituted carborano-coumarin derivatives with potential applications in pharmaceuticals were facilely prepared in moderate to high yields with excellent chemoselectivity and regioselectivity. A plausible reaction mechanism including CO insertion, electrophilic B-H metalation, alkyne insertion and reductive elimination was proposed.

Synthesis of indolo- and pyrrolo[1,2-a]quinoxalinones through a palladium-catalyzed oxidative carbonylation of the C2 position of indole.

A methodology that involves the Pd-catalyzed direct C(sp2)-H bond carbonylation of the C2 position of indole has been introduced for the synthesis of indolo[1,2-a]quinoxalin-6(5H)-ones. The methodology developed herein was used for the synthesis of pyrrolo[1,2-a]quinoxalin-4(5H)-ones. The reaction of N-substituted 2-(1H-indol-1-yl)anilines or 2-(1H-pyrrol-1-yl)anilines and carbon monoxide in the presence of Pd(OCOCF3)2 as a catalyst and Cu(OAc)2 as an oxidant in toluene at 80 °C forms the corresponding quinoxalinones as exclusive products in good yields. The catalytically active C-H activated intermediate Pd complex was isolated and characterized for the first time which on exposure to CO gas in toluene at 80 °C gave the corresponding quinoxalinone derivative. On the basis of isolation of the intermediate, a possible mechanism has been proposed for the C-H activated direct carbonylative annulation of 2-(5-methoxy-1H-indol-1-yl)-N,4-dimethylaniline.

Polystyrene-Supported Palladium (Pd@PS)-Catalyzed Carbonylative Annulation of Aryl Iodides Using Oxalic Acid as a Sustainable CO Source for the Synthesis of 2-Aryl Quinazolinones.

An efficient and convenient strategy for the synthesis of diversely substituted quinazolinones from o-carbamoyl/cyano aniline and aryl iodides using oxalic acid as a CO source under polystyrene supported palladium (Pd@PS) nanoparticles (NPs) catalyzed conditions has been developed. In this study, oxalic acid has been employed as safe, economic, environmentally benign, sustainable and bench-stable, solid CO surrogate under Double-Layer-Vial (DLV) system for the synthesis of 2-aryl quinazolinones. This methodology does not require any special high-pressure equipment like autoclaves, microwaves, etc. Moreover, a simple procedure for catalyst preparation, catalyst recyclability, easy handling of reaction, additive and base-free generation of CO, excellent to good yields and vast substrate scope are the additional features of developed protocol.

Carbonylative Synthesis of 3-Substituted Thiochromenones via Rhodium-Catalyzed [3 + 2 + 1] Cyclization of Different Aromatic Sulfides, Alkynes, and Carbon Monoxide.

We have developed a rhodium-catalyzed carbonylative annulation methodology for the direct preparation of thiochromenones. With nonactivated aromatic sulfides and terminal alkynes as the substrates, the desired sulfur-containing six-membered heterocycles were prepared effectively via [3 + 2+1]-type annulation.

A highly efficient heterogeneous palladium-catalyzed carbonylative annulation of 2-aminobenzamides with aryl iodides leading to quinazolinones

The first heterogeneous carbonylative annulation of 2-aminobenzamides with aryl iodides was achieved in N,N-dimethylformamide (DMF) at 120 °C under 10 bar of carbon monoxide by using an MCM-41-immobilized bidentate phosphine palladium(II) complex [MCM-41-2P-Pd(OAc)2] as catalyst and 1,8-diazabicycloundec-7-ene (DBU) as base, yielding a wide variety of quinazolinone derivatives in good to excellent yields. The new heterogeneous palladium catalyst can easily be prepared by a simple procedure from commercially readily available reagents, and recovered by filtration of the reaction solution, and recycled up to eight times without significant loss of activity.

Selectivity Controlled Palladium-Catalyzed Carbonylative Synthesis of Propiolates and Chromenones from Phenols and Alkynes.

An interesting selectivity-controlled palladium-catalyzed oxidative carbonylation procedure for the synthesis of propiolates and chromenones has been developed. Starting from phenols and alkynes, under slightly different conditions, various propiolates and chromenones can be isolated in moderate to good yields. Additionally, this also presents the first example of direct carbonylative annulation of nonpreactivated phenols and terminal alkynes to produce chromenones.

Diastereoselective C-H carbonylative annulation of aliphatic amines: a rapid route to functionalized γ-lactams.

A palladium(ii)-catalysed C(sp3)-H carbonylation of free(NH) secondary aliphatic amines to 2-pyrrolidinones is described. A correlation between the nature of the carboxylate ligand and the diastereoselectivity and yield of the process was observed. As such, under these optimal conditions a range of aliphatic amines were converted to the corresponding trans-4,5-disubstituted 2-pyrrolidines with good d.r. and yield.

Palladium catalyzed carbonylative annulation of the C(sp2)–H bond of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-triazol-3-amines to quinazolinones

Pd(ii) catalyzed direct C-H carbonylative annulation of N,1-diaryl-1H-tetrazol-5-amines and N,4-diaryl-4H-1,2,4-triazol-3-amines gave the corresponding triazole and tetrazole fused quinazolinones in good yields. This methodology offers a convenient method for the synthesis of these important heterocyclic scaffolds in a highly atom economical process. On the mechanistic aspect weakly nucleophilic triazole and tetrazole moieties function as both directing as well as intramolecular nucleophiles. The catalytically active C-H activated intermediate dimeric Pd complex was isolated and characterized which on exposure to CO gas gave the corresponding tetrazole fused quinazolinone derivative. On the basis of isolation of the intermediate and observed kinetic isotope effects, a mechanism has been proposed for the C-H activated direct carbonylative annulation reaction.

Pd-catalysed carbonylative annulation of salicylaldehydes with benzyl chlorides usingN-formylsaccharin as a CO surrogate

A highly efficient synthesis of 3-arylcoumarins by Pd-catalysed carbonylative cyclisation of salicylaldehydes with benzyl chlorides usingN-formylsaccharin as a CO source is developed.

Selective Synthesis of 3-Arylbenzo-1,2,3-triazin-4(3H)-ones and 1-Aryl-(1H)-benzo-1,2,3-triazoles from 1,3-Diaryltriazenes through Pd(0) Catalyzed Annulation Reactions.

Pd(0) catalyzed carbonylative annulation reaction of 1-(2-iodophenyl)-3-aryltriaz-1-enes in the presence of DABCO and 1 atm of carbon monoxide in toluene at 80 °C gave the corresponding 3-arylbenzo-1,2,3-triazin-4(3H)-ones with high selectivity and in excellent yields. Substrate scope of this reaction is demonstrated with 24 examples with various halo, alkyl, and alkoxy substituents on either of the aromatic rings. Bromo substituted triazenes were less reactive as starting materials toward the carbonylative annulation reaction and yielded 3-arylbenzo-1,2,3-triazin-4(3H)-ones in good to moderate yields in the presence of only xantphos as an additive. In the absence of CO (under N2 atmosphere), the reaction did not proceed, and only starting material was recovered. However, in the presence of catalytic amount of CO or in the presence of Ph3P in catalytic amounts as additives, the reactions proceeded to yield the corresponding 1-aryl-(1H)-benzo-1,2,3-triazoles selectively in good yields. On the basis of control experiments, a plausible reaction mechanism for the selective formation of 3-arylbenzo-1,2,3-triazin-4(3H)-ones in the presence of CO and1-aryl-(1H)-benzo-1,2,3-triazoles in the absence of CO through a common intermediate was proposed.

Rhodium-catalyzed Carbonylative Annulation of 2-Bromobenzylic Alcohols with Internal Alkynes Using Furfural via β-Aryl Elimination

In spite of the significant progress made in transformations of unstrained benzylic (tert-)alcohols through β-aryl elimination, catalytic carbonylation has not yet been developed extensively because alkoxycarbonylation is probably favored over β-aryl elimination. In this letter, we report on the rhodium(I)-catalyzed carbonylative annulation of α,α-dimethyl-(2-bromoaryl)methanols with internal alkynes using furfural leading to the formation of indenones. The key to the success of the reaction is the timely generation of the carbonyl source via the decarbonylation of furfural.

Iridium-Catalyzed and Ligand-Controlled Carbonylative Synthesis of Flavones from Simple Phenols and Internal Alkynes.

Flavones are important natural products with diverse biological activities. In this study, a novel procedure for the carbonylative synthesis of flavones has been developed by using simple phenols and internal alkynes as the substrates. Various flavones were isolated in moderate to good yields with excellent regioselectivity and functional group tolerance by using an iridium catalyst system. Notably, this is the first example of direct carbonylative annulation of non-preactivated phenols and alkynes to produce flavones, with the choice of ligand proving to be critical for the success of this transformation.

Rhodium(I)‐Catalyzed Carbonylative Annulation of Iodobenzenes with Strained Olefins and 4‐Octyne in the Presence of Furfural Involving ortho‐C–H Bond Cleavage

AbstractThe rhodium(I)‐catalyzed carbonylative annulation of iodobenzenes with strained olefins in the presence of furfural as a carbonyl source, accompanied by ortho‐C–H bond cleavage, is reported. The use of 4‐octyne in place of strained olefins also leads to the formation of the corresponding inden‐9‐one. The timely release of the carbonyl moiety via the rhodium‐catalyzed decarbonylation of furfural plays a decisive role in this reaction.magnified image