Ru- and Co-Catalyzed Intermolecular Carbonyl-Alkyne Metathesis Reactions of 1H-Indene-1,2,3-triones with Internal Alkynes

The catalyst-dependent intermolecular carbonyl-alkyne metathesis (CAM) reaction of 1H-indene-1,2,3-triones with internal alkynes was realized using Ru and Co catalysts. 2-(2-Oxo-1,2-diphenylethylidene)-1H-indene-1,3(2H)-dione derivatives were obtained using a Ru catalyst, whereas S-alkyl 2-(1,3-dioxo-1,3-dihydro-2H-inden-2-ylidene)-2-phenylethanethioates were prepared using a Co catalyst. These transformations led to the synthesis of α,β-unsaturated carbonyl compounds with a broad substrate scope, excellent regiocontrol, and gram-scale amenability. This catalytic strategy using a Co or Ru catalyst has rarely been described for other established CAM catalysts.

Construction of 4-Acyl-2-quinolones through Sc(OTf)3-Catalyzed Ring-Closing Alkyne-Carbonyl Metathesis

An atom-economical protocol to construct densely substituted 4-acyl-2-quinolones from N-(2-alkynylphenyl)-α-ketoamides has been developed through Sc(OTf)₃-catalyzed ring-closing alkyne-carbonyl metathesis. Mechanistic experimental studies support that coordinative interaction between Sc(OTf))₃ and the substrate, the formation of an oxetene intermediate, and an electrocyclic ring-opening of the oxetene might be involved.

Synthesis of imidazo[1,2-a]benzoazepines by alkyne-carbonyl-metathesis

Imidazo[1,2-a]benzoazepines were prepared in good yields by combination of Pd catalyzed cross coupling reactions with alkyne-carbonyl metathesis (ACM).

Ag(I)-Promoted homo-dimerization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes via a [4 + 2] cycloaddition of benzopyrylium ions: access to structurally unique naphthalenes

Herein we report a Ag(I)-promoted homo-dimerization of 2-(alk-2-yn-1-onyl)-1-alkynylbenzenes for the synthesis of structurally novel and functionalized naphthalene derivatives. This transformation exhibits a broad scope for the alkyl as well as aryl groups present on alkynes. Observations made from control experiments suggest the possible mechanism as (i) the homo-dimerization of the in situ generated benzopyrylium ion intermediates through a head-tail [4 + 2] cycloaddition, followed by (ii) the competitive ring-opening vs. decarbonylative aromatization of the adduct to give formylated and deformylated naphthalenes, respectively.

Iron-catalyzed alkyne-carbonyl metathesis for the synthesis of 6,7-dihydro-5H-dibenzo[c,e]azonines

The synthesis of nine-membered rings via alkyne-carbonyl metathesis is reported. The alkyne and acetal units contained in a biaryl substrate undergo the intramolecular alkyne-carbonyl metathesis reaction under FeCl₃-catalysis to furnish the unexplored 6,7-dihydro-5H-dibenzo[c,e]azonines. The method provides an alternative to existing routes to nine-membered rings with cheap, non-toxic iron catalysts and milder conditions.

I2 -Promoted Intramolecular Oxidative Cyclization of Butenyl Anilines: A Facile Route to Benzo[b]azepines

A metal-free approach for the synthesis of seven-membered N-heterocycles has been developed by the I₂ -promoted intramolecular cross-coupling/annulation of butenyl anilines. This cyclization reaction involves C-H activation and C-C bond formation and exhibits good functional group tolerance. A series of benzo[b]azepine derivatives are obtained in moderate to good yields.

Iron-catalyzed carboarylation of alkynes via activation of π-activated alcohols: rapid synthesis of substituted benzofused six-membered heterocycles

An Fe(OTf)3-catalysed carboarylation of alkynes is reported for the straightforward synthesis of densely substituted 1,2-dihydroquinolines from N-propargyl anilides and π-activated alcohols. The reaction provides a new method for the synthesis of highly substituted benzofused six-membered heterocycles by the formation of two carbon-carbon bonds and one ring in a single step. The power of the methodology was further extended to the synthesis of substituted chromene and thiochromene derivatives in high yields. In addition, substituted quinoline derivatives were also achieved in a single step in the presence of FeCl3 through detosylation/aromatisation. A number of control experiments have been performed and a plausible mechanism has also been proposed to explain the formation of the products.

Phosphine-Catalyzed α-Umpolung-Aldol Reaction for the Synthesis of Benzo[ b]azapin-3-ones

A novel phosphine-catalyzed intermolecular cyclization between 2-sulfonamidobenzaldehyes and ynones is reported. This methodology serves as a conduit for the construction of benzo[ b]azepin-3-ones in good to excellent yields under mild conditions. The resulting 2-benzylidene moieties are formed exclusively in the E-configuration. Mechanistically, this unusual annulation occurs through a phosphine-catalyzed α-umpolung addition, followed by an aldol reaction. One of the benzo[ b]azepin-3-one products was converted to the core structure of 3-amino-[ a]benzazepin-2-one-1-alkanoic acids, many of which function as angiotensin-converting enzyme inhibitors.

Copper-catalyzed one-pot domino reactions via C–H bond activation: synthesis of 3-aroylquinolines from 2-aminobenzylalcohols and propiophenones under metal–organic framework catalysis

A Cu₂(OBA)₂(BPY) metal–organic framework was utilized as a productive heterogeneous catalyst for the synthesis of 3-aroylquinolines via one-pot domino reactions of 2-aminobenzylalcohols with propiophenones. This Cu-MOF was considerably more active towards the one-pot domino reaction than a series of transition metal salts, as well as nano oxide and MOF-based catalysts. The MOF-based catalyst was reusable without a significant decline in catalytic efficiency. To the best of our knowledge, the transformation of 2-aminobenzylalcohols to 3-aroylquinolines was not previously reported in the literature, and this protocol would be complementary to previous strategies for the synthesis of these valuable heterocycles.

Cu₂(OBA)₂(BPY) metal–organic framework was utilized as a productive heterogeneous catalyst for the synthesis of 3-aroylquinolines via one-pot domino reactions of 2-aminobenzylalcohols with propiophenones.

A one pot three-component reaction for the preparation of dihydroquinolines with two different ketones and aromatic amines

A three component reaction with two different ketones and aromatic amines was firstly investigated. The difference in reactivity between ordinary ketones and ketone esters allowed for the production of 1,2-DHQs efficiently. The possible Skraup reaction with 2 equiv. of the same ketones was prohibited due to the fast formation of imines.

Synthesis and Reactivity of Propargylamines in Organic Chemistry

Propargylamines are a versatile class of compounds which find broad application in many fields of chemistry. This review aims to describe the different strategies developed so far for the synthesis of propargylamines and their derivatives as well as to highlight their reactivity and use as building blocks in the synthesis of chemically relevant organic compounds. In the first part of the review, the different synthetic approaches to synthesize propargylamines, such as A³ couplings and C-H functionalization of alkynes, have been described and organized on the basis of the catalysts employed in the syntheses. Both racemic and enantioselective approaches have been reported. In the second part, an overview of the transformations of propargylamines into heterocyclic compounds such as pyrroles, pyridines, thiazoles, and oxazoles, as well as other relevant organic derivatives, is presented.

Synthesis of 3-acylquinolines through Cu-catalyzed double C(sp3)–H bond functionalization of saturated ketones

A novel synthesis of 3-acylquinolines through Cu-catalyzed one-pot reactions of 2-aminoaryl aldehydes/ketones with inactivated ketones featured with double C(sp³)–H bond functionalization is presented.

Metal free carboamination of internal alkynes – an easy access to polysubstituted quinolines

A synergistic Brønsted acid catalyst was used to intermolecularly generate vinyl cations for a C–C bond formation – Schmidt rearrangement – sequence.

Novel routes to quinoline derivatives from N-propargylamines

A walk around the new avenue to the synthesis of quinoline derivatives from N-propargylamines.

Barluenga's reagent with HBF4as an efficient catalyst for alkyne-carbonyl metathesis of unactivated alkynes

Barluenga's reagent (IPy₂BF₄, Py = pyridine) treated with HBF₄efficiently catalyzes the inter- and intramolecular alkyne-carbonyl metathesis of unactivated alkynes. This work represents the first catalytic application of the Barluenga's reagent.

Synthesis of polysubstituted 1,2-dihydroquinolines and indoles via cascade reactions of arylamines and propargylic alcohols catalyzed by FeCl3·6H2O

Syntheses of 1,2-dihydroquinolines from arylamines and propargylic alcohols via cascade Friedel–Crafts-type reaction and 6-endo-trig hydroamination catalyzed by FeCl₃·6H₂O are described.

Iron(iii) halide or iodine-promoted synthesis of 3-haloindene derivatives from o-alkynylarene chalcones

The treatment of o-alkynylarene chalcones with ferric halides/iodine affords 3-haloindene derivatives in good yields.

Synthesis of quinoxalines or quinolin-8-amines from N-propargyl aniline derivatives employing tin and indium chlorides

The utility of stannous chloride dihydrate as well as indium/InCl₃ in combination with “ortho-nitrogen”-N-propargylanilines for the construction of either quinoxaline- or quinolin-8-amine-scaffolds is demonstrated. Depending on the nature of the alkyne, different bicyclic nitrogen heterocycles are formed under aerobic conditions.

Fe-promoted oxidative cyclization of α-benzoylthioformanilides for the synthesis of 2-benzoylbenzothiazoles

This protocol has the advantages of short reaction times, moderate to good yields, convenient manipulation, and high selectivities.