Vilsmeier Reaction of Enaminones: Efficient Synthesis of Halogenated Pyridin-2(1H)-ones

Switchable Regioselective C-H Activation/Annulation of Acrylamides with Alkynes for the Synthesis of 2-Pyridones

A catalyst-based switchable regioselective C-H activation/annulation of acrylamides with propargyl carbonates has been developed, delivering C5 or C6 alkenyl substituted 2-pyridones. This robust protocol proceeds with a broad substrate scope and good functional group tolerance under redox-neutral reaction conditions. More significantly, this reaction is highly effective with previously challenging unsymmetrical alkynes, including unbiased alkyl-alkyl substituted alkynes, with perfect and switchable regioselectivity. Additionally, mechanistic studies and DFT calculations were performed to shed light on the switchable regioselectivity.

Tf2O-Mediated Cyclization of α-Acyl-β-(2-aminopyridinyl)acrylamides: Access to N-Substituted 4H-Pyrido[1,2-a]pyrimidin-4-imines

A facile and efficient direct synthesis of N-substituted 4H-pyrido[1,2-a]pyrimidin-4-imines is developed from α-acyl-β-(2-aminopyridinyl)acrylamides mediated by triflic anhydride (Tf₂O) in the presence of 2-chloropyridine. This amide activation protocol features mild reaction conditions, simple execution, excellent yields, and high chemoselectivity, and is also applied to the synthesis of substituted 4H-pyrido[1,2-a]pyrimidin-4-ones via a practical one-pot procedure.

In-Water Synthesis of 5-Thiolated 1,2,3-Triazoles from β-Thioenaminones by Diazo Transfer Reaction

The synthesis of 1,2,3-triazoles with a sulfur-based side chain has been accessed with the metal-free annulation reactions of readily available β-thiolated enaminones and tosyl hydrazine. By these reactions with water as the only medium, a broad array of 5-thiolated 1,2,3-triazoles have been synthesized with generally good to excellent yields. Except using TMEDA (N,N,N',N'-tetramethylethylenediamine) as the only base promoter, not any other catalyst or additive is required, thus providing an efficient and environmentally benign method for useful 1,2,3-triazole synthesis.

Structure-Based Design and Synthesis of 3-Amino-1,5-dihydro-4H-pyrazolopyridin-4-one Derivatives as Tyrosine Kinase 2 Inhibitors

We report herein the discovery and optimization of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one TYK2 inhibitors. High-throughput screening against TYK2 and JAK1-3 provided aminoindazole derivative 1 as a hit compound. Scaffold hopping of the aminoindazole core led to the discovery of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one derivative 3 as a novel chemotype of TYK2 inhibitors. Interestingly, initial SAR study suggested that this scaffold could have a vertically flipped binding mode, which prompted us to introduce a substituent at the 7-position as a moiety directed toward the solvent-exposed region. Introduction of a 1-methyl-3-pyrazolyl moiety at the 7-position resulted in a dramatic increase in TYK2 inhibitory activity, and further optimization led to the discovery of 20. Compound 20 inhibited IL-23-induced IL-22 production in a rat PD assay, as well as inhibited IL-23 signaling in human PBMC. Furthermore, 20 showed selectivity for IL-23 signaling inhibition against GM-CSF, demonstrating the unique cytokine selectivity of the novel TYK2 inhibitor.

PBr3-mediated [5 + 1] annulation of α-alkenoyl-α-carbamoyl ketene-S,S-acetals: access to substituted pyridine-2,6(1H,3H)-diones

Facile and efficient synthesis of substituted pyridine-2,6(1H,3H)-diones via an intramolecular [5 + 1] annulation of readily available α-alkenoyl-α-carbamoyl ketene-S,S-acetals mediated by phosphorus bromide under very mild is developed.

Vilsmeier reagent-mediated synthesis of 6-[(formyloxy)methyl]-pyrazolopyrimidines via a one-pot multiple tandem reaction

Vilsmeier reagent-mediated synthesis of pyrazolopyrimidines.

Fabrication of Ag/γ-Fe2O3@TiO2 hollow magnetic core–shell nanospheres as highly efficient catalysts for the synthesis of β-enaminones

Herein, we describe a method to prepare hollow magnetic mesoporous sphere catalysts (Ag/γ-Fe₂O₃@meso-TiO₂).

Vilsmeier cyclization of α-acetyl-α-aroyl ketene-N,S-acetals: direct and efficient synthesis of halogenated pyridin-2(1H)-ones

An efficient synthetic route to 3-aroyl-5-formyl-4-halo pyridin-2(1H)-ones has been developed via Vilsmeier cyclization of 2-(ethylthio(arylamino)methylene)-1-alkylbutane-1,3-dione.

Tandem halogenation/Michael-initiated ring-closing reaction of α,β-unsaturated nitriles and activated methylene compounds: one-pot diastereoselective synthesis of functionalized cyclopropanes

An efficient one-pot synthetic route to highly substituted cyclopropanes has been developed from readily available α,β-unsaturated nitriles and doubly activated methylene compounds under very mild conditions in a highly diastereoselective manner, which involves halogenation, Michael addition and intramolecular ring-closing reaction sequences.

Formal [4+2] annulation of enaminones and cyanomethyl sulfur ylide: one-pot access to polysubstituted pyridin-2(1H)-ones

One-pot synthesis of polysubstituted pyridin-2(1H)-ones by formal [4+2] annulation of enaminones and cyanomethyl sulfur ylide is described involving sequential nucleophilic vinylic substitution, intramolecular nucleophilic cyclization and dealkylation reactions.

BF3·Et2O-mediated intramolecular cyclization of unsaturated amides: convenient synthesis of dihydroquinolin-2-one-BF2 complexes

A facile and efficient synthesis of substituted dihydropyridone–BF₂ complexes is developed via intramolecular cyclization of α-acyl acrylamides and α-acyl cinnamamides mediated by BF₃·Et₂O, respectively.

An efficient method for the construction of polysubstituted 4-pyridones via self-condensation of β-keto amides mediated by P2O5 and catalyzed by zinc bromide

A self-condensation cyclization reaction mediated by phosphorus pentoxide (P2O5) and catalyzed by zinc bromide (ZnBr2) is presented for the synthesis of polysubstituted 4-pyridones and 2-pyridones from β-keto amides. A variety of β-keto amides are used in this approach, and a wide range of functionalized 4-pyridones and 2-pyridones were obtained in good to excellent yields. When employing the N-aryl β-keto amides as the substrates in this protocol, 4-pyridones are resulted, however, when using N-aliphatic-substituted β-keto amides as the partners of N-aryl β-keto amides under the same conditions, 2-pyridones are afforded.

Synthesis of pyridin-2(1H)-one derivatives via enamine cyclization

The nucleophilic vinylic substitution reaction of the aliphatic enaminone 3-dimethylamino-2-formyl acrylonitrile 1 with the nucleophiles malononitrile and ethyl cyanoacetate produced the two unusual reaction adducts 3a and 3b in good to moderate yield under milder reaction conditions. Upon reaction with aromatic amines, these adducts yielded enamines 4 and 5, which eventually cyclized in the presence of base to produce the novel pyridin-2(1H)-one derivatives 8 and 9.

A Stereodivergent Approach for Accessing Both C2,8a-Syn and C2,8a-Anti Relative Stereochemical Manifolds in the Lepadin Family via a TiCL(4)-Promoted Aza-[3 + 3] Annulation

Details in developing a stereodivergent approach to the lepadin family and establishing an entry to both C2,8a-syn and C2,8a-anti relative stereochemical manifolds through a common intermediate are described here. This works paves a foundation for constructing all members of the lepadin family, which consists of three subsets based on an array of interesting relative configurations. These efforts underline the prominence of aza-[3 + 3] annulation as a unified strategy in alkaloid synthesis.