4-Chloro-3-(trifluoroacetyl)coumarin as a novel building block for the synthesis of 7-(trifluoromethyl)-6H-chromeno[4,3-b]quinolin-6-ones

Synthesis of Purines and Related Molecules by Cyclization ­Reactions of Heterocyclic Enamines

A great variety of pharmacologically relevant fluorinated purine analogues are available by cyclization reactions of heterocyclic enamines with 1,3-dielectrophiles. The reactions usually proceed with excellent regioselectivities. As electrophiles, 1,3-diketones, enaminones or 3-chloro-2-en-1-ones were used. Other synthetic strategies are based on inverse-electron-demand Diels–Alder reactions of heterocyclic enamines with triazines. Purine analogues were further functionalized by transition-metal-catalyzed CH-coupling reactions or oxidative cyclizations, giving rise to more complex polycyclic products. Amidino-C-glycosides in their reactions with 1,3-dielectrophiles afforded pyrimidine-C-glycosides. Multicomponent reactions of heterocyclic enamines afforded complex products, including spirocyclic derivatives.

1 Introduction

2 1,3-Diketones

3 Enaminones

4 3-Chloro-2-en-1-ones

5 Triazines

6 Transition-Metal-Catalyzed Functionalizations

7 Pyrimidine-C-Nucleosides

8 Multicomponent Reactions

9 Conclusions

The synthesis, biological evaluation and fluorescence study of chromeno[4,3-b]pyridin/quinolin-one derivatives, the backbone of natural product polyneomarline C scaffolds: a brief review

This review presents the synthesis, biological and fluorescence study of chromeno[4,3-b]pyridin/quinolin-ones via classical reactions including metal-catalyzed and green reaction protocols.

Aerobic, metal-free synthesis of 6H-chromeno[4,3-b]quinolin-6-ones

A Friedländer-based method for transition-metal free, aerobic synthesis of chromene-fused quinolinones is reported. The coupling of 4-hydrocoumarins and 2-aminobenzyl alcohols proceeds in the presence of acetic acid solvent and oxygen oxidant, affording 6H-chromeno[4,3-b]quinolin-6-ones in good to excellent yields. The reactions are tolerant of functionalities such as alkyl, methoxy, bromo, chloro, and N-heterocycle. Isosteric cyclic 1,3-diketones and 2-amino acetophenones also give fused quinolinones under reaction conditions. The method herein offers a rapid and benign synthesis of hitherto challenging N-heterocycles. To our best knowledge, such a convenient pathway to obtain chromene-fused quinolinones have not been known in the literature.

A Friedländer-based method for transition-metal free, aerobic synthesis of chromene-fused quinolinones is reported.

Novel 6a,12b-Dihydro-6H,7H-chromeno[3,4-c] chromen-6-ones: Synthesis, Structure and Antifungal Activity

A new series of coumarin derivatives, 7-hydroxy-7-(trifluoromethyl)-6a,12b-dihydro-6H,7H-chromeno[3,4-c]chromen-6-ones 3a–p, were synthesized via Michael addition, transesterification and nucleophilic addition from the reaction of 3-trifluoroacetyl coumarins and phenols in the presence of an organic base. The products were characterized by infrared spectroscopy (IR), hydrogen nuclear magnetic resonance spectroscopy (¹H-NMR), carbon nuclear magnetic resonance spectroscopy (¹³C-NMR) and high-resolution mass spectrometer (HRMS). Single crystal X-ray analysis of compounds 3a and 3n clearly confirmed their assigned chemical structures and their twisted conformations. Compound 3a crystallized in the orthorhombic system, Pbca, in which a = 8.6244(2) Å, b = 17.4245(4) Å, c = 22.5188(6) Å, α = 90°, β = 90°, γ = 90°, v = 3384.02(14) ų, and z = 8. In addition, the mycelial growth rate method was used to examine the in vitro antifungal activities of the title compounds 3a–p against Fusarium graminearum and Fusarium monitiforme at 500 µg/mL. The results showed that compound 3l exhibited significant anti-Fusarium monitiforme activity with inhibitory index of 84.6%.

Synthesis and Biological Evaluation of Novel Thiazolyl-Coumarin Derivatives as Potent Histone Deacetylase Inhibitors with Antifibrotic Activity

New histone deacetylases (HDAC) inhibitors with low toxicity to non-cancerous cells, are a prevalent issue at present because these enzymes are actively involved in fibrotic diseases. We designed and synthesized a novel series of thiazolyl-coumarins, substituted at position 6 (R = H, Br, OCH₃), linked to classic zinc binding groups, such as hydroxamic and carboxylic acid moieties and alternative zinc binding groups such as disulfide and catechol. Their in vitro inhibitory activities against HDACs were evaluated. Disulfide and hydroxamic acid derivatives were the most potent ones. Assays with neonatal rat cardiac fibroblasts demonstrated low cytotoxic effects for all compounds. Regarding the parameters associated to cardiac fibrosis development, the compounds showed antiproliferative effects, and triggered a strong decrease on the expression levels of both α-SMA and procollagen I. In conclusion, the new thiazolyl-coumarin derivatives inhibit HDAC activity and decrease profibrotic effects on cardiac fibroblasts.

Establishing the concept of aza-[3 + 3] annulations using enones as a key expansion of this unified strategy in alkaloid synthesis

A successful enone version of an intramolecular aza-[3 + 3] annulation reaction is described here. Use of piperidinium trifluoroacetate salt as the catalyst and toluene as the solvent appears to be critical for a successful annulation. We also demonstrated for the first time that microwave irradiation can accelerate aza-[3 + 3] annulation reactions. An attempt to expand the scope of the enone aza-[3 + 3] annulation was made in the form of propyleine synthesis as a proof of concept. While synthesis of the enone annulation precursor was successfully accomplished, the annulation proved to be challenging and was only modestly successful.