Ruthenium-catalyzed oxidative coupling and cyclization between 2-aminobenzyl alcohol and secondary alcohols leading to quinolines

2-Aminobenzyl alcohol is oxidatively coupled and cyclized with secondary alcohols in dioxane at 80°C in the presence of a catalytic amount of RuCl₂(PPh₃)₃ and KOH along with 1-dodecene as a sacrificial hydrogen acceptor to give the corresponding quinolines in good yields. The cyclization is applicable to a wide range of alkyl(aryl) and alkyl(alkyl) carbinols. The catalytic pathway seems to be proceeded via a sequence involving initial oxidation of both substrates to carbonyl compounds, cross aldol reaction, and cyclodehydration.     

Dicopper complexes catalyzed coupling/cyclization of 2‐bromobenzoic acids with amidines leading to quinazolinones

Dicopper(I) complexes {Cu₂(bpnp)(CH₃CN)₄}(PF₆)₂] ( 2 ), [{Cu₂(bpnp)(CH₃CN)₄}(BAr₄^F)₂] ( 3 ) and [Cu₂(bpnp)Cl₂] ( 4 ) were prepared from the complexation of [Cu(CH₃CN)₄](PF₆) with 2,7‐bis(2‐pyridyl)‐1,8‐naphthyridine (bpnp) followed by anion metathesis and treatment of chloride sequentially. The X‐ray structural analysis of 4 indicates the molecule to have a twofold axis passing through the Cu₂Cl₂ core, which has the shape of a butterfly, and that the Cu atom is tetrahedrally coordinated with in a Cl₂N₂ donor set. In preliminary experiments 2 was found to be an effective catalyst in the coupling/cyclization of 2‐bromobenzoic acids with amidines, providing the corresponding quinazolinones in good yields. Copyright © 2014 John Wiley & Sons, Ltd.     

Ligand‐free CuI‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with formamide leading to pyrimidinones

β‐Bromo‐α,β‐unsaturated amides were coupled and cyclized with formamide in DMF at 100°C in the presence of a catalytic amount of a copper(I) salt along with a base to give the corresponding pyrimidinones in good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Microwave‐assisted copper powder‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with amidine hydrochlorides leading to pyrimidinones

β‐Bromo‐α,β‐unsaturated amides are coupled and cyclized with amidine hydrochlorides using microwave irradiation in the presence of a catalytic amount of copper powder and a base to give the corresponding pyrimidinones in good yields. Copyright © 2015 John Wiley & Sons, Ltd.     

Palladium‐catalyzed carbonylative cyclization of 3‐bromoallyl alcohols leading to furan‐2(5H)‐ones

3‐Bromoallyl alcohols are carbonylatively cyclized under carbon monoxide pressure in toluene in the presence of a catalytic amount of Pd(OAc)₂ and PPh₃ along with Na₂CO₃ to give furan‐2(5H)‐ones in good yields. Copyright © 2012 John Wiley & Sons, Ltd.     

Palladium‐catalyzed cyclization of β‐bromo‐α,β‐unsaturated ketones with arylhydrazines leading to 3‐substituted 1‐aryl‐1 H‐pyrazoles

β‐Bromo‐α,β‐unsaturated ketones are condensed with arylhydrazines to form hydrazones, which are in situ intramolecularly cyclized into 3‐substituted 1‐aryl‐1 H‐pyrazoles under a catalytic system of Pd(OAc)₂/1,3‐bis(diphenylhosphino)propane (dppp)/NaO^tBu. Copyright © 2012 John Wiley & Sons, Ltd.     

Ruthenium-catalyzed reductive cyclization of nitroarenes with trialkylamines leading to quinolines

Nitroarenes react with trialkylamines in the presence of a catalytic amount of a ruthenium catalyst together with tin(II) chloride dihydrate at 180 °C in an aqueous medium (toluene–H₂O) to afford the corresponding quinolines in moderate to good yields. The catalytic pathway seems to be proceeded via a sequence involving initial reduction of nitroarenes to anilines, alkyl group transfer from alkylamines to anilines to form an imine, dimerization of imine, and heterocyclization.     

Palladium‐catalyzed three‐component cyclization of 2‐bromocyclohex‐1‐enecarboxylic acids with carbon monoxide and arylhydrazines leading to 2‐anilinohydroisoindoline‐1,3‐diones

2‐Bromocyclohex‐1‐enecarboxylic acids are carbonylatively cyclized with arylhydrazines or their hydrochlorides in tetrahydrofuran at 120 °C under carbon monoxide pressure in the presence of a catalytic amount of PdCl₂ and 1,3‐bis(diphenylphosphino)propane along with Et₃N to give 2‐anilinohydroisoindoline‐1,3‐diones. Copyright © 2015 John Wiley & Sons, Ltd.     

Palladium-catalyzed oxidative coupling of trialkylamines with aryl iodides leading to alkyl aryl ketones

A new, simple method for selectively synthesizing alkyl aryl ketones has been developed by palladium-catalyzed oxidative coupling of trialkylamines with aryl iodides. In the presence of PdCl(2)(MeCN)(2), TBAB, and ZnO, a variety of aryl iodides underwent an oxidative coupling reaction with tertiary amines and water to afford the corresponding alkyl aryl ketones in moderate to excellent yields. It is noteworthy that this method is the first example of using trialkylamines as the carbonyl sources for constructing alkyl aryl ketone skeletons.     

Palladium‐catalyzed carbonylative cyclization of β‐bromo‐α,β‐unsaturated carboxylic acids with primary amines leading to N‐alkylmaleimides

Cyclic β‐bromo‐α,β‐unsaturated carboxylic acids are carbonylatively cyclized with primary amines under carbon monoxide pressure in MeCN in the presence of a catalytic amount of PdCl₂(PPh₃)₂ to give N‐alkylmaleimides. Copyright © 2012 John Wiley & Sons, Ltd.     

CuI/amino acid‐catalyzed coupling and cyclization of β‐bromo‐α,β‐unsaturated amides with terminal alkynes leading to (3Z)‐3‐alkylidenepyrrol‐1‐ones

β‐Bromo‐α,β‐unsaturated amides are coupled and cyclized with terminal alkynes in DMF at 110 °C in the presence of a catalytic amount of CuI and amino acid along with a base to give the corresponding (3Z)‐3‐alkylidenepyrrol‐1‐ones in moderate to good yields. Copyright © 2013 John Wiley & Sons, Ltd.     

A palladium-catalyzed C–H functionalization route to ketones via the oxidative coupling of arenes with carbon monoxide

We describe the development of a new palladium-catalyzed method to generate ketones via the oxidative coupling of two arenes and CO. This transformation is catalyzed by simple palladium salts, and is postulated to proceed via the conversion of arenes into high energy aroyl triflate electrophiles. Exploiting the latter can also allow the synthesis of unsymmetrical ketones from two different arenes.

A palladium catalyzed route to prepare aryl ketones from their two fundamental building blocks, two arenes and carbon monoxide, is described.     

Palladium‐catalyzed carbonylative cyclization of 1‐bromoallyl bromides with anilines leading to 1‐aryl‐1H‐pyrrol‐2(5H)‐ones

1‐Bromoallyl bromides are carbonylatively cyclized with anilines under carbon monoxide pressure in DMF in the presence of a catalytic amount of a palladium catalyst along with a base to give the corresponding 1‐aryl‐1H‐pyrrol‐2(5H)‐ones in moderate to good yield. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

CuI/amino acid catalysis in coupling and cyclization of β‐bromo‐α,β‐unsaturated carboxylic acids with terminal alkynes leading to alkylidenefuranones

β‐Bromo‐α,β‐unsaturated carboxylic acids are coupled and cyclized with terminal alkynes in DMF at 110°C in the presence of a catalytic amount of CuI and amino acid along with a base to give alkylidenefuranones in good yields. Similar reaction under microwave irradiation also gave alkylidenefuranones in higher yields. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium‐catalyzed carbonylative cyclization of β‐bromo‐α,β‐unsaturated carboxylic acids with 2,2‐dimethylhydrazine leading to 1‐(dimethylamino)‐1H‐pyrrole‐2,5‐diones

β‐Bromo‐α,β‐unsaturated carboxylic acids are carbonylatively cyclized with 2,2‐dimethylhydrazine under carbon monoxide pressure in THF in the presence of a catalytic amount of a palladium catalyst along with a base to give 1‐(dimethylamino)‐1H‐pyrrole‐2,5‐diones. Copyright © 2014 John Wiley & Sons, Ltd.     

Bismuth‐catalyzed cyclization of amino‐1,6‐enynes

Bi(OTf)₃ effectively catalyzed the cyclization of amino‐1,6‐enynes, leading to bicyclic amine and cyclopentadienyl amino compounds. The selectivity of the products depends on the substitution pattern of the olefinic moiety. ¹⁹F NMR trace experiment of the reaction and other results indicate a novel alkynophilicity of the bismuth species. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:644–648, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20490     

Cyclocondensation reactions of heterocyclic carbonyl compounds XII. The double course of cyclization of 3‐(2‐aminobenzyl)‐1,2‐dihydro‐quinoxaline‐2‐one

The cyclocondensation reaction of compound 1 in boiling hydrochloric acid had an unexpected course. Instead of supposed 5,11‐dihydro‐quinoxalino[2,3‐b]quinoline 6a , 2‐(indol‐2‐yl)‐benzimidazole 4 was isolated as the major product.     

Ruthenium‐catalyzed formation of quinolines via reductive cyclization of nitroarenes with tris(3‐hydroxypropyl)amine in an aqueous medium

Nitroarenes react with tris(3‐hydroxypropyl)amine in an aqueous medium (dioxane/H₂O) at 180° in the presence of a catalytic amount of a ruthenium catalyst and tin(II) chloride along with isopropanol as hydrogen donor to afford the corresponding quinolines in good yields. The presence of tin(II) chloride is essential for the formation of quinolines. A reaction pathway involving initial reduction of nitroarenes to anilines, propanol group transfer from tris(3‐hydroxypropyl)amine to anilines to form 3‐anilino‐1‐propanols, N‐alkylation of anilines by 3‐anilino‐1‐propanol to form 1,3‐dianilinopropane and intramolecular heteroannulation of 1,3‐dianilinopropane is proposed for this catalytic process.     

Silver-mediated C-H activation: oxidative coupling/cyclization of N-arylimines and alkynes for the synthesis of quinolines

A silver-mediated tandem protocol for the synthesis of quinolines involving the oxidative coupling/cyclization of N-arylimines and alkynes has been developed. We demonstrated that scenario-dependent metalation could occur either at the ortho C-H bond of an N-arylimine through protonation-driven enhancement of acidity or at the terminal C-H bond of an alkyne by virtue of the carbophilic π-acidity of silver. The diverse set of mechanistic manifolds implemented with a single type of experimental protocol points toward the importance of stringent reactivity analysis of each individual potentially reactive molecular site. Importantly, the direct arene C-H bond activation provides a unique and distinct mechanistic handle for the expansion of reactivity paradigms for silver. As expected, the protocol allows for the incorporation of both internal and terminal alkynes into the products, and in addition, both electron-withdrawing and -donating groups are tolerated on N-arylimines, thus enabling the vast expansion of substituent architectures on quinoline framework. Further, an intriguing phenomenon of structural isomerization and chemical bond cleavage has been observed for aliphatic internal alkynes.