Evaluation of Anti-Inflammatory and Anti-Tubercular Activity of 4-Methyl-7-Substituted Coumarin Hybrids and Their Structure Activity Relationships

Four sets of previously synthesized 4-methyl-7-substituted coumarin derivatives were screened for their in vitro anti-inflammatory and anti-tubercular activities. The anti-inflammatory potential of 3a-t, 5a-o, 6a-n, and 7a-f synthesized compounds was evaluated by an anti-denaturation assay using diclofenac sodium as the reference standard. Evaluation of the anti-tuberculous activity of the mentioned compounds was performed by the Resazurin test method against four different TB strains using rifampicin and isoniazid as reference drugs. Based on the anti-inflammatory results, compounds 3o, 5f, 6c, and 7d proved to be the most active compounds in their respective series. Additionally, compounds 3k-n, 5b-d, 6d-f, 6k, 7a, and 7f were found to be the most potent anti-tuberculous agents. In fact, most of the screened compounds exhibited promising activity profiles compared to the respective standard drugs. The structure-activity connections revealed a few intriguing aspects, indicating that the presence of electron-donating and nitrogen-rich fragments boost the anti-inflammatory effects of the examined compounds. However, the presence of electron-withdrawing substituents was required to boost the anti-tubercular activity of the evaluated compounds.

Synthesis of 7-Aminocoumarins from 7-Hydroxycoumarins via Amide Smiles Rearrangement

N-Substituted 7-aminocoumarins can be synthesized from readily available 7-hydroxycoumarins via alkylation with α-bromoacetamides and subsequent tandem O → N Smiles rearrangement-amide hydrolysis. The key rearrangement sequence proceeds under mild conditions to provide convenient access to various N-alkyl and N-aryl products in moderate to high yields. The process is operationally simple, inexpensive, transition-metal-free, and can be telescoped into a one-pot process.

Synthesis of Rhodamines and Rosamines Using 3,6-Difluoroxanthone as a Common Intermediate

Rhodamines and structurally similar rosamines are some of the most highly utilized tools for molecular imaging experiments. We report a general and high-yielding route to produce 18 examples of rhodamines and rosamines, including tetramethylrhodamine, rhodamine B, and Janelia Fluor 549, from a single xanthone intermediate, 3,6-difluoroxanthone. Spectroscopic studies revealed trends in fluorophore efficiency based on substitution patterns at the 3'-, 6'-, and 9'-positions, providing insights to aid future designs of rhodamines/rosamines.

Palladium-Catalyzed Cross-Couplings by C-O Bond Activation

Although palladium-catalyzed cross-coupling of aryl halides and reactive pseudohalides has revolutionized the way organic molecules are constructed today across various fields of chemistry, comparatively less progress has been made in the palladium-catalyzed cross-coupling of less reactive C-O electrophiles. This is despite the fact that the use of phenols and phenol derivatives as bench-stable cross-coupling partners has been well-recognized to bring about major advantages over aryl halides, such as (1) natural abundance of phenols, (2) avoidance of toxic halides, (3) orthogonal cross-coupling conditions, (4) prefunctionalization of phenolic substrates by electrophilic substitution or C-H functionalization, (5) ready availability of phenols from a different pool of precursors than aryl halides. In this review, we present an overview of recent advances made in the field of palladium-catalyzed cross-coupling of C-O electrophiles with a focus on (1) catalytic systems, (2) reaction type, and (3) class of C-O coupling partners. Although the field has been historically dominated by nickel catalysis, it is now evident that the use of more versatile, more functional group tolerant and highly active palladium catalysts supported by appropriately designed ancillary ligands enables the cross-coupling with improved substrate scope and generality, and likely represents a practical solution to the broadly applicable cross-coupling of various C-O bonds across diverse chemical disciplines. The review covers the period through June 2020.

NIXANTPHOS: a highly active ligand for palladium catalyzed Buchwald–Hartwig amination of unactivated aryl chlorides

The NIXANTPHOS-based catalyst outperformed the parent ligand Xantphos in Pd catalyzed amination reaction of aryl chlorides at room temperature.

MoO2Cl2(DMF)2 catalyzed microwave assisted reductive cyclisation of nitroaromatics into dibenzodiazepines

Microwave induced, MoO₂Cl₂(DMF)₂ catalyzed synthesis of novel dibenzodiazepine scaffolds with potential biocidal activity.