Annulation Of Alkynes Research Articles

ChemInform Abstract: Dehydrative C—H/N—OH Functionalizations in H2O by Ruthenium(II) Catalysis: Subtle Effect of Carboxylate Ligands and Mechanistic Insight.

A ruthenium(II) complex derived from the electron-deficient aromatic carboxylic acid 3-(F3C)C6H4CO2H proved to be a highly efficient catalyst for dehydrative alkyne annulation by NH-free hydroxamic acids in water. The C–H/N–OH functionalization occurred with excellent positional selectivity as well as ample substrate scope, setting the stage for effective intermolecular alkenylations of hydroxamic acids. Detailed mechanistic studies were suggestive of a kinetically relevant C–H metalation by carboxylate assistance along with subsequent migratory alkyne insertion, reductive elimination, and intramolecular oxidative addition.

ChemInform Abstract: Palladium‐Catalyzed Annulation of Alkynes with ortho‐Halide‐Containing Benzyl Alcohols in Aqueous Medium.

AbstractOrtho‐brom benzyl alcohols are also applicable in these reactions with slightly lower yields.

ChemInform Abstract: One‐Pot Synthesis of Highly Fluorescent Pyrido[1,2‐a]indole Derivatives through C—H/N—H Activation: Photophysical Investigations and Application in Cell Imaging.

AbstractA simple one‐pot protocol for the Pd‐catalyzed oxidative annulation of internal alkynes with indoles to form pyridooxindole derivatives is presented.

Metal‐Free [2+2+1] Annulation of Alkynes, Nitriles and Nitrogen Atoms from Iminoiodanes for Synthesis of Highly Substituted Imidazoles

AbstractBoron trifluoride nitrile complexes promote oxidative [2+2+1] annulations of alkynes, nitriles and N‐atoms from iminoiodanes to give the corresponding 2,4‐disubstituted and 2,4,5‐trisubstituted N‐tosylimidazoles in moderate to good yields with high regioselectivities.magnified image

ChemInform Abstract: Silver‐Mediated Alkyne Annulations by C—H/P—H Functionalizations: Step‐Economical Access to Benzophospholes.

Silver-mediated alkyne annulations by secondary phosphine oxides (SPOs) or arylphosphinates via C–H/P–H functionalization provided versatile access to substituted benzo[b]phospholes in a step-economical fashion.

Hypervalent-iodine-mediated cascade annulation of diarylalkynes forming spiro heterocycles under metal-free conditions.

An unusual reaction featuring the cascade annulation of internal alkynes to afford spiro heterocycles as the products has been realized for the first time with a hypervalent iodine reagent as the only oxidant. This unprecedented process encompasses not only two sequential C-N/C-O-bond formations, but also the insertion of a carbonyl oxygen, all in one pot under metal-free conditions.

ChemInform Abstract: Chiral Phosphines in Nucleophilic Organocatalysis

AbstractReview: 117 refs.

Cyclometallated ruthenium(ii) complexes with ditopic thienyl–NHC ligands: syntheses and alkyne annulations

Cycloruthenation of thienyl–NHC ligands and subsequent alkyne annulations allow for a facile preparation of unusual aza-heterocyclic-thiophenes.

Dehydrative C-H/N-OH functionalizations in H2O by ruthenium(II) catalysis: subtle effect of carboxylate ligands and mechanistic insight.

A ruthenium(II) complex derived from the electron-deficient aromatic carboxylic acid 3-(F3C)C6H4CO2H proved to be a highly efficient catalyst for dehydrative alkyne annulation by NH-free hydroxamic acids in water. The C-H/N-OH functionalization occurred with excellent positional selectivity as well as ample substrate scope, setting the stage for effective intermolecular alkenylations of hydroxamic acids. Detailed mechanistic studies were suggestive of a kinetically relevant C-H metalation by carboxylate assistance along with subsequent migratory alkyne insertion, reductive elimination, and intramolecular oxidative addition.

Palladium-catalyzed annulation of alkynes with ortho-halide-containing benzyl alcohols in aqueous medium.

The Pd-catalyzed annulations of ortho-halide-containing benzyl alcohols with alkynes for the synthesis of indenones were achieved in aqueous Triton X-100 micelles with good yields and wide substrate scopes. Moreover, the indenones obtained in this procedure can be further functionalized to form some more synthetic useful derivatives via an environmental-friendly way.

Exploring a unique reactivity of N-heterocyclic carbenes (NHC) in rhodium(III)-catalyzed intermolecular C-H activation/annulation.

Disclosed herein is the unique conjugative role of N-heterocyclic carbene (NHC) ligands as a directing group in aromatic C-H activation, coupled with a facile NHC-alkenyl annulative reductive elimination which guided the Rh(III)-catalyzed intermolecular annulations of imidazolium salts and alkynes under ambient conditions leading to structurally important imidazo[1,2-a]quinolinium motifs.

ChemInform Abstract: Ruthenium‐Catalyzed Oxidative Alkyne Annulation by C—H Activation on Ketimines.

AbstractCarboxylate‐assisted ruthenium catalysis enables the oxidative annulation of alkynes by ketimines to form isoquinoline derivatives (III).

Nickel(0)‐Catalyzed Enantioselective Annulations of Alkynes and Arylenoates Enabled by a Chiral NHC Ligand: Efficient Access to Cyclopentenones

AbstractCyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel‐catalyzed reductive [3+2] cycloaddition of α,β‐unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1‐symmetric N‐heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.

Nickel(0)-catalyzed enantioselective annulations of alkynes and arylenoates enabled by a chiral NHC ligand: efficient access to cyclopentenones.

Cyclopentenones are versatile structural motifs of natural products as well as reactive synthetic intermediates. The nickel-catalyzed reductive [3+2] cycloaddition of α,β-unsaturated aromatic esters and alkynes constitutes an efficient method for their synthesis. Here, nickel(0) catalysts comprising a chiral bulky C1-symmetric N-heterocyclic carbene ligand were shown to enable an efficient asymmetric synthesis of cyclopentenones from mesityl enoates and internal alkynes under mild conditions. The bulky NHC ligand provided the cyclopentenone products in very high enantioselectivity and led to a regioselective incorporation of unsymmetrically substituted alkynes.

ChemInform Abstract: Ruthenium(II)‐Catalyzed Synthesis of Isochromenes by C—H Activation with Weakly Coordinating Aliphatic Hydroxyl Groups.

Cationic ruthenium(II) complexes have been employed for the highly effective oxidative annulation of alkynes with benzyl alcohols to deliver diversely decorated isochromenes. The hydroxyl-directed C-H/O-H functionalization process proceeded efficiently under an atmosphere of air. Detailed mechanistic studies were indicative of a kinetically relevant C-H metalation.

ChemInform Abstract: Modular Assembly of Ring‐Fused and π‐Extended Phenanthroimidazoles via C—H Activation and Alkyne Annulation.

AbstractA series of ring‐fused and π‐extended phenanthroimidazoles are synthesized via rhodium(III)‐catalyzed C—H activation and alkyne annulation.

One-pot synthesis of highly fluorescent pyrido[1,2-a]indole derivatives through C-H/N-H activation: photophysical investigations and application in cell imaging.

We describe a straightforward strategy for the synthesis of strongly fluorescent pyridoindoles by Pd-catalyzed oxidative annulations of internal alkynes with C-3 functionalized indoles through CH/NH bond activation in a one-pot tandem process. Mechanistic investigations reveal the preferential activation of NH indole followed by CH activation during the cyclization process. Photophysical properties of pyridoindoles exhibited the highest fluorescence quantum yield of nearly 80 %, with emission color varying from blue to green to orange depending on the substructures. Quantum mechanical calculations provide insights into the observed photophysical properties. The strong fluorescence of the pyrido[1,2-a]indole derivative has been employed in subcellular imaging, which demonstrates its localization in the cell nucleus.

Chiral phosphines in nucleophilic organocatalysis.

This review discusses the tertiary phosphines possessing various chiral skeletons that have been used in asymmetric nucleophilic organocatalytic reactions, including annulations of allenes, alkynes, and Morita–Baylis–Hillman (MBH) acetates, carbonates, and ketenes with activated alkenes and imines, allylic substitutions of MBH acetates and carbonates, Michael additions, γ-umpolung additions, and acylations of alcohols.

ChemInform Abstract: Palladium‐Catalyzed Annulation of Internal Alkynes in Aqueous Medium.

AbstractIt is demonstrated, that a reusable palladacycle efficiently catalyzes the carbo‐ and heteroannulation of internal alkynes with a wide variety of functionalized aryl halides in aqueous media.

ChemInform Abstract: Rhodium(III)‐Catalyzed C—H Activation and Indole Synthesis with Hydrazone as an Auto‐Formed and Auto‐Cleavable Directing Group.

An efficient, practical, and external-oxidant-free indole synthesis from readily available aryl hydrazines was developed, by using hydrazone as a directing group for RhIII-catalyzed CH activation and alkyne annulation. The hydrazone group was formed by in situ condensation of hydrazines and CO source, whereas its NN bond was served as an internal oxidant, for which we termed it as an auto-formed and auto-cleavable directing group (DGauto). This method needs no step for pre-installation and post-cleavage of the directing group, making it a quite easily scalable approach to access unprotected indoles with high step economy. The DGauto strategy was also applicable for isoquinoline synthesis. In addition, synthetic utilities of this chemistry for rapid assembly of π-extended nitrogen-doped polyheterocycles and bioactive molecules were demonstrated.