Tandem Reactions of 1,2-Allenic Ketones Leading to Substituted Benzenes and α,β-Unsaturated Nitriles

Synthesis of α-allenic aldehydes/ketones from homopropargylic alcohols using a visible-light irradiation system

A visible-light irradiation tandem oxidative aryl migration/carbonyl formation reaction, mediated by K₂S₂O₈ and visible-light photoredox catalysis, has been discovered. The presented transformation provides a straightforward access to important α-allenic aldehyde/ketone derivatives from readily available homopropargylic alcohol derivatives in a regioselective manner of 1,4-aryl shift concomitant with carbonyl formation. The operational simplicity and broad substrate scope demonstrate the great potential of this method for the synthesis of highly functional α-allenic aldehyde/ketone derivatives.

Insights into the chemistry and therapeutic potential of acrylonitrile derivatives

Acrylonitrile is a fascinating scaffold widely found in many natural products, drugs, and drug candidates with various biological activities. Several drug molecules such as entacapone, rilpivirine, teriflunomide, and so forth, bearing an acrylonitrile moiety have been marketed. In this review, diverse synthetic strategies for constructing desired acrylonitriles are discussed, and the different biological activities and medicinal significance of various acrylonitrile derivatives are critically evaluated. The information gathered is expected to provide rational guidance for the development of clinically useful agents from acrylonitriles.

Regioselective Synthesis of Tetrasubstituted Benzenes via Co-Catalyzed Cycloaddition of Alkynyl Ketones and 2-Acetylpyridines

A Co(II)-catalyzed cycloaddition reaction of alkynyl ketones and 2-acetylpyridines using 2,2'-bipyridine as the ligand has been developed. These reactions have been realized through Co-catalyzed reductive coupling of two molecules of 2-acetylpyridine followed by regioselective insertion of the alkynone. It is the first example of regioselective cyclotrimerization of one molecule of alkyne and two molecules of monoketone to polysubstituted benzene derivatives in good to excellent yields. A mechanism involving the formation of a cobaltacyclopentane via homocoupling of 2-acetylpyridines is proposed, and it is supported by the DFT calculations.

Asymmetric Aza-Claisen Rearrangement between Enantioenriched α-Chiral Allylamines and Allenones

An unprecedented asymmetric aza-Claisen rearrangement between enantioenriched α-chiral allylamines and allenones was found to proceed in the absence of catalysts and additives at room temperature. The rearrangement, followed by hydrolysis, provides convenient access to structurally diverse δ-chiral β-diketones in good to excellent yields with excellent retention of enantiopurity. This protocol proved powerful for the construction of an all-carbon quaternary stereocenter with high enantiopurity.

Palladium-Catalyzed Cascade Reactions of δ-Ketonitriles with Arylboronic Acids: Synthesis of Pyridines

This study presents the first example of the Pd-catalyzed cascade reactions of 5-oxohexanenitrile with arylboronic acids, affording important synthon 2-methylpyridines that can be further translated through C(sp³)-H functionalization to construct pyridine derivatives. Furthermore, this chemistry allows 5-oxo-5-arylpentanenitrile to react with arylboronic acids to provide unsymmetrical 2,6-diarylpyridines. This protocol paves the way for the practical and atom economical syntheses of valuable pyridines with broad functional groups in moderate to excellent yields under mild conditions.

Facilitating Myers–Saito cyclization through acid-triggered tautomerization for the development of maleimide-based antitumor agents

Enyne-allene compounds undergo Myers–Saito cyclization at physiological temperature to generate diradical intermediates that are capable of inducing DNA damage and cell death.

Base-promoted direct synthesis of functionalized N-arylindoles via the cascade reactions of allenic ketones with indoles

A convenient Cs2CO3-promoted cascade benzannulation reaction of allenic ketones with indoles was achieved for the synthesis of functionalized N-arylindole derivatives under transition-metal-free conditions. A series of readily available starting materials can undergo the process successfully. It represents a practical method for the construction of N-arylindole scaffolds with high atom economy.

Lewis base catalyzed regioselective cyclization of allene ketones or α-methyl allene ketones with unsaturated pyrazolones

A nitrogen-containing Lewis base catalyzed highly regioselective [4 + 2] cycloaddition of allene ketones or α-methyl allene ketones with unsaturated pyrazolones has been disclosed to give the corresponding tetrahydropyrano [2,3-c] pyrazoles in moderate to good yields under mild conditions. High regioselectivity, 100% atom-economy, broad substrate scope and good functional group tolerance are attractive features of this process and make it a practical and versatile transformation.

AlCl3 catalyzed coupling of N-benzylic sulfonamides with 2-substituted cyanoacetates through carbon-nitrogen bond cleavage

A new cross-coupling reaction of N-benzylic sulfonamides with 2-substituted cyanoacetates for the synthesis of 2-substituted benzylbenzene was reported. In the presence of AlCl₃, a broad range of N-benzylic sulfonamides reacted smoothly with 2-substituted cyanoacetates to afford structurally diverse benzylbenzenes in moderate to excellent yields. The conversion could be enlarged to gram-scale efficiently. The practicability of this approach was further manifested in the synthesis of a related bioactive agent with high anti-inflammatory activity.

Synthesis of diversely substituted 2-(furan-3-yl)acetates from allenols through cascade carbonylations

Novel synthesis of diversely substituted 2-(furan-3-yl)acetatesviapalladium-catalyzed one-pot multi-component reactions of allenols, aryl iodides, alcohols, and carbon monoxide has been developed. Moreover, the 2-(furan-3-yl)acetates obtained were found to be ready intermediates for the construction of the biologically significant naphtho[1,2-b]furan-5-ol scaffold.

One-pot cascade reactions of 1-arylpenta-3,4-dien-2-ones leading to 2-arylphenols and dibenzopyroanones

A one-pot tandem reaction of 1-arylpenta-3,4-dien-2-ones with activated ketones allowed for an efficient synthesis of 2-arylphenols. Moreover, this reaction was found to be also compatible and combinable with Pd-catalyzed C–H activation and carbonylation of the in situ formed 2-arylphenols to provide dibenzopyranones.

3-(4-Chlorobenzoyl)-6-(4-chlorophenyl)-2,4-dimethylbenzonitrile

In the title compound, C₂₂H₁₅Cl₂NO, the terminal chloro­benzene rings are oriented at 44.51 (15) and 86.06 (17)° with respect to the central polysubstituted benzene ring, and make a dihedral angle of 49.48 (17)°with each other. In the crystal, mol­ecules are linked by weak C—H⋯O and C—H⋯N inter­actions.

Cu(OAc)2/TFA-promoted formal [3 + 3] cycloaddition/oxidation of enamines and enones for synthesis of multisubstituted aromatic amines

New strategies for the oxidative cycloaddition of enones with enamines are developed. These cycloaddition reactions directly afford substituted aromatic amines, which are important in organic chemistry, in moderate to good yield. Cu(OAc)(2)/TFA is shown to be essential to achieve high reaction efficiency.

5,6-Dimethyl-4-phenyl-2H-pyran-2-one

In the title compound, C(13)H(12)O(2), the dihedral angle between the pyran-one and phenyl rings is 57.55 (9)°. In the crystal, the mol-ecules are linked by π-π stacking inter-actions between the parallel pyran-one rings of neighboring mol-ecules with distances of 3.5778 (11) Å and 3.3871 (11) Å between the planes. C-H⋯O interactions also occur.