Palladium-Catalyzed -Michael-Type Hydroamination of -(Quinolin-8-yl)acrylamide with 2-Pyridones.

Here we report a palladium-catalyzed -Michael-type hydroamination of -(quinolin-8-yl)acrylamide with 2-pyridones. The use of a palladium catalyst enables the α-addition of 2-pyridones, resulting in the formation of a range of -substituted 2-pyridone carboxamides with yields ranging from 10% to 80%. Derivatization of the products highlights the utility of this transformation.

Modular synthesis of 3,3-disubstituted oxindoles from nitrones and acrylic acids.

We developed a modular synthesis for 3,3-disubstituted oxindoles, utilising readily accessible nitrones and acrylic acids. This approach facilitates the preparation of a diverse array of oxindoles through the variation of the starting materials. We demonstrated the applicability of this method through a gram-scale reaction and a synthesis of esermethole.

Palladium-Catalyzed -Michael-Type (Hetero)arylation of Acrylamides.

This paper reports a direct α-(hetero)arylation of acrylamides through an inverse electron-demand nucleophilic addition, specifically an -Michael-type addition. The introduction of a quinolyl directing group facilitates the nucleophilic addition of (hetero)arenes to the α-position of acrylamides. The quinolyl directing group effectively suppresses undesired β-hydrogen elimination and is removable for subsequent derivatization.

Rhodium-catalysed additive-free alkoxycarbonylation of indoles: 2,4,6-trimethylbenzoic acid-based carbonate anhydrides as a versatile alkoxycarboxyl source.

We report a CO-free approach to indole-2-carboxylic esters: rhodium-catalysed C(2)-alkoxycarbonylation of indoles with 2,4,6-trimethylbenzoic acid-based carbonate anhydrides. Selective C-O bond cleavage of the anhydrides facilitates the introduction of various alkoxycarbonyl groups. Control experiments suggest that merging a rhodium catalyst and KI promotes the formation of the RhI species.

Rhodium-catalysed additive-free carbonylation of benzamides with diethyl dicarbonate as a carbonyl source.

Phthalimides are prevalent in numerous pharmaceuticals, prompting various phthalimide syntheses through C-H activation. Nevertheless, the necessity for stoichiometric additives limits their practicality and versatility. Herein, we introduced diethyl dicarbonate as a carbonyl source for an additive-free carbonylation of benzamides.

Diastereo- and Enantioselective Reductive Mannich-type Reaction of α,β-Unsaturated Carboxylic Acids to Ketimines: A Direct Entry to Unprotected β -Amino Acids.

Stereoselective construction of unprotected β-amino acids is a significant challenge owing to the lack of methods for the catalytic generation of highly enantioenriched carboxylic acid enolates. In this study, a novel copper-catalyzed diastereo- and enantioselective reductive Mannich-type reaction of α,β-unsaturated carboxylic acids was developed, which provides a direct and scalable synthetic method for enantioenriched β -amino acids with vicinal stereogenic centers. The protocol features in situ generation of transiently protected carboxylic acids by a hydrosilane and their diastereo- and enantioselective reductive coupling with ketimines.

Rhodium-catalysed decarbonylative C(sp)-H alkylation of indolines with alkyl carboxylic acids and carboxylic anhydrides under redox-neutral conditions.

We developed a rhodium-catalysed decarbonylative C(sp)-H alkylation method for indolines. This reaction facilitates the use of alkyl carboxylic acids and their anhydrides as a cheap, abundant and non-toxic alkyl source under redox-neutral conditions, featuring the introduction of a primary alkyl chain, which cannot be addressed by previous radical-mediated decarboxylative reaction. Through a mechanistic investigation, we revealed that an initially formed C-7 acylated indoline was transformed into the corresponding alkylated indoline a decarbonylation process.

Rhodium-Catalyzed C(sp)-H Alkoxycarbonylation/Acylation of Indolines with Anhydrides as a Carbonyl Source.

We developed rhodium-catalyzed alkoxylcarbonylation/acylation of indolines using anhydrides as a safe and easy-to-handle carbonyl source. This catalytic process represents an additive- and CO-free carbonylation, establishing a simple and straightforward protocol for synthesizing C7-carbonylated indolines. Notably, this reaction provides a successful example of C-H acylation of indolines that results in the formation of α-branched ketones, which were difficult to prepare by previously reported analogous catalytic reactions.

Copper-Catalyzed Enantioselective Reductive Aldol Reaction of α,β-Unsaturated Carboxylic Acids to Alkyl Aryl Ketones: Silanes as Activator and Transient Protecting Group.

The first enantioselective reductive aldol reaction of unprotected α,β-unsaturated carboxylic acids was developed by employing a copper/bisphosphine catalyst. The reaction features in situ protection and activation of an α,β-unsaturated carboxylic acid by a hydrosilane. The copper enolate formed in situ reacts with an alkyl aryl ketone to afford the β-hydroxy carboxylic acid with excellent enantioselectivity (up to 99 % ee).

Dealkoxylation of -alkoxyamides without an external reductant driven by Pd/Al cooperative catalysis.

Lewis acid-assisted palladium-catalysed dealkoxylation of N-alkoxyamides has been developed. This reaction proceeded smoothly with a range of N-alkoxyamides in the absence of an external reductant, thereby establishing a convenient and reductant-free protocol. In addition, a gram-scale reaction could be achieved.

Synthesis of unsymmetrical benzils via palladium-catalysed α-arylation-oxidation of 2-hydroxyacetophenones with aryl bromides.

A diverse set of unsymmetrically substituted benzils were facilely synthesised by a cross-coupling reaction between 2-hydroxyacetophenones and aryl bromides in the presence of a palladium catalyst. Experimental studies suggested a reaction mechanism involving a one-pot tandem palladium-catalysed α-arylation and oxidation, where aryl bromides play a dual role as mild oxidants as well as arylating agents.

Ruthenium-catalysed cyclisation reactions of 1,11-dien-6-ynes leading to biindenes.

1,2-Bis(2-allylphenyl)ethynes undergo cycloisomerisation reactions in the presence of Cp*Ru(ii) catalysts to produce 2,2'-dimethyl-3H,3'H-1,1'-biindenes. On the other hand, tandem ring-closing metathesis of 1,2-bis(2-allylphenyl)ethynes using the Hoveyda-Grubbs 2nd generation catalyst led to the formation of 2,2'-unsubstituted biindenes. Various symmetrical and unsymmetrical bicyclic dienes were prepared by these ruthenium-based cyclisation methods.

Synthesis of Fused and Linked Benzofurans from 2-Alkynylphenol Derivatives through Rhodium(I)-catalyzed Domino-type Addition Reactions.

A rhodium(I)-catalyzed domino-type sequential 5-/5- cyclization reaction of [(2-acylphenyl) ethynyl]phenols produces indene/benzofuran-fused alcohols. A moderate asymmetric induction is observed when chiral diphosphine ligands are used for rhodium. Indene/indole-fused compounds are synthesized by a similar reaction of [(2-acetylphenyl)ethynyl]anilines.

Synthesis of indole-fused heteroacenes by cascade cyclisation involving rhodium(ii)-catalysed intramolecular C-H amination.

Heteroacenes are potentially important materials for organic electronics and their syntheses are of topical interest. Herein we report the development of a catalytic, redox-neutral reaction for the synthesis of the 5,10-dihydroindolo[3,2-b]indole class of heteroacenes. 2-[(2-Azidophenyl)ethynyl]anilines undergo cascade cyclisation by gold(i)/rhodium(ii) relay catalysis.

Enhancement of tetragonal anisotropy and stabilisation of the tetragonal phase by Bi/Mn-double-doping in BaTiO ferroelectric ceramics.

To stabilise ferroelectric-tetragonal phase of BaTiO, the double-doping of Bi and Mn up to 0.5 mol% was studied. Upon increasing the Bi content in BaTiO:Mn:Bi, the tetragonal crystal-lattice-constants a and c shrank and elongated, respectively, resulting in an enhancement of tetragonal anisotropy, and the temperature-range of the ferroelectric tetragonal phase expanded.

Rhodium(i)-catalysed skeletal reorganisation of benzofused spiro[3.3]heptanes via consecutive carbon-carbon bond cleavage.

Skeletal reorganisation of benzofused spiro[3.3]heptanes has been achieved using rhodium(i) catalysts. The reaction of benzofused 2-(2-pyridylmethylene)spiro[3.

Rhodium(i)-catalysed intermolecular alkyne insertion into (2-pyridylmethylene)cyclobutenes.

Cyclobutenes with 2-pyridylmethylene groups at the 3 position underwent an intermolecular alkyne insertion reaction in the presence of a rhodium(i) catalyst at 170 °C to afford substituted benzenes. Among the different 2-pyridylmethylene groups examined, 3-methyl-2-pyridyl derivatives showed superior activity and readily coupled with various alkynes, including sterically demanding, heteroaromatic and terminal alkynes.

Ruthenium-Catalyzed Cycloisomerization of 2,2'-Diethynyl- biphenyls Involving Cleavage of a Carbon-Carbon Triple Bond.

A ruthenium complex catalyzes a new cycloisomerization reaction of 2,2'-diethynylbiphenyls to form 9-ethynylphenanthrenes, thereby cleaving the carbon-carbon triple bond of the original ethynyl group. A metal-vinylidene complex is generated from one of the two ethynyl groups, and its carbon-carbon double bond undergoes a [2+2] cycloaddition with the other ethynyl group to form a cyclobutene. The phenanthrene skeleton is constructed by the subsequent electrocyclic ring opening of the cyclobutene moiety.

A rhodium(I)-catalysed formal intramolecular C-C/C-H bond metathesis.

Phenylcyclobutanes underwent skeletal reorganisation in the presence of Wilkinson's catalyst to afford indanes through a cascade process involving chelation-assisted C-C bond cleavage and intramolecular C-H bond cleavage.

Rhodium-catalysed arylative annulation of 1,4-enynes with arylboronic acids.

The rhodium(I)-catalysed arylative annulation of 1,4-enynes with arylboronic acids was investigated. The reaction was found to proceed via an addition-1,4-rhodium migration-addition sequence, affording the corresponding 1,1-disubstituted 3-(arylmethylene)indanes.

Gold(I)-catalyzed ring-expanding spiroannulation of cyclopropenones with enynes.

The gold(I)-catalyzed ring-expanding spiroannulation of cyclopropenones with enynes is reported here. A molecule of water is incorporated into the products during the spiroannulation to afford spirocyclic cyclopentenones containing an alcohol functionality.

Synthesis of tetrasubstituted benzenes via rhodium(I)-catalysed ring-opening benzannulation of cyclobutenols with alkynes.

A formal [4 + 2] annulation occurs between 1,3-disubstituted cyclobutenols and internal alkynes in the presence of rhodium(I) catalysts to afford 1,2,3,5-tetrasubstituted benzenes. These benzannulation products are generated through dehydration of the initially formed cyclohexadienols.

Synthesis of dibenzoheteropines of group 13-16 elements via ring-closing metathesis.

The ring-closing metathesis (RCM) of bis(2-vinylphenyl)silanes in the presence of the second-generation Hoveyda-Grubbs catalyst in toluene at 100 °C afforded dibenzo[b,f]silepines in excellent yields. Other dibenzoheteropines of group 13-16 elements were also prepared via the RCM of the corresponding heteroatom-tethered dienes.

Synthesis of phthalazinones via palladium(II)-catalysed intramolecular oxidative C-H/C-H cross-coupling of N'-methylenebenzohydrazides.

A palladium(II)-catalysed intramolecular oxidative C-H/C-H cross-coupling of N'-methylenebenzohydrazides to phthalazin-1(2H)-ones has been developed. This cyclization is believed to mechanistically proceed via electrophilic ortho-palladation and subsequent C-arylation of the carbon-nitrogen double bond.