Photocatalyzed Synthesis of a Schiff Base via C-N Bond Formation: Benzyl Alcohol as Sustainable Surrogates of Aryl Aldehydes.

The advancement of photocatalytic techniques has enabled green chemical synthesis through visible-light-mediated photochemical oxidation under mild conditions. A novel approach under visible-light conditions was facilitated by eosin-Y for the reaction between substituted benzyl alcohols and anilines, resulting in the synthesis of diverse Schiff bases. This innovative method is emphasized for its environmentally friendly nature, lack of metal catalysts, cost-effectiveness, and nontoxic characteristics.

A green synthesis of pyrimido[4,5-b]quinolines and pyrido[2,3-d]pyrimidines via a mechanochemical approach.

A cost-effective and competent approach has been established for the synthesis of pyrimido[4,5-b]quinolines and pyrido[2,3-d]pyrimidines via a multicomponent reaction of 1,3 diketones (dimedone, barbituric acid, and Meldrum's acid), 6-aminouracil and aromatic aldehyde, through mechanochemical synthesis using a ball-mill. This transformation involves a one pot, catalyst-free, and solvent-free pathway to develop the desired products under mild reaction conditions.

Metal-Free Photoredox Catalyzed Sulfonylation of Phenylhydrazines with Thiols.

The sulfonylation method stands out as a simple and efficient approach for synthesizing sulfonamides. Despite the advancements in constructing the sulfonamide framework, the potential use of phenyl hydrazine as an amination source remains unexplored. Herein, we report a metal-free, environment-friendly photoredox-catalyzed sulfonylation of phenylhydrazines using thiols, employing MeCN:H2O as a green solvent and eosin Y as a photoredox catalyst. This strategy exhibits a broad substrate scope and good functional group compatibility, including hetero(aryl) as well as aliphatic phenylhydrazines. Finally, this protocol also demonstrated good application for the synthesis of pharmaceutical analogues.

Photo-triggered C-arylation of active-methylene compounds with diazonium salts via an electron donor-acceptor (EDA) complex.

The elucidation of the C-arylation of active methylene compounds under visible light conditions without a photocatalyst presents an intellectual challenge. The photo-induced C-arylation of active methylene compounds via electron donor-acceptor (EDA) complexes shows a strategic path for the synthesis of pharmacologically relevant compounds. This expansive and efficacious methodology facilitates C-arylation under environmentally conscientious conditions, exhibiting exemplary compatibility with diverse functional groups and yielding numerous compounds. This environmentally sustainable transformation underscores the merits of the procedural simplicity and benign reaction conditions. Notably, all resultant products were judiciously derived from active methylene compounds and diazonium salts through the intermediacy of the EDA complex.

Photoinduced, Metal-Free Hydroacylation of Aromatic Alkynes for Synthesis of α,ß-Unsaturated Ketones via C(sp3)-H Functionalization.

Despite the notable advancements made over the past decade in achieving carbon-carbon bonds by transition-metal-catalyzed cross-coupling processes, metal-free cross-coupling reactions for hydroacylation of aromatic alkynes via C(sp3)-H functionalization are still rare and highly desired. Here we report a metal-free reliable approach for the synthesis of α,ß-unsaturated ketones (chalcones) via C(sp3)-H functionalization using MeCN:H2O as green solvent, Eosin Y as organic photocatalyst, and ambient air as oxidant. More significantly, this strategy can effectively transform a variety of methyl arenes and aromatic alkynes into the desired product. With high atom efficiency, use of green solvents, metal-free nature, environmental friendliness, and visible light as a renewable energy source, this method is compatible with biologically active molecules.

Visible-light-absorbing C-N cross-coupling for the synthesis of hydrazones involving C(sp2)-H/C(sp3)-H functionalization.

An efficient C-N cross-coupling approach for the synthesis of hydrazones was developed through C(sp2)-H and C(sp3)-H functionalization of indole and methylarene under visible light irradiation using photocatalyst eosin Y, ethanol:water as a green solvent and atmospheric air as an oxidant. With the aid of eosin Y, the C-H bonds of indole and methylarenes were activated followed by coupling with arylhydrazines. The procedure was applied to a wide variety of substrates with good functional group compatibility, offering a creative way to make hydrazones from inexpensive and easily accessible raw materials. The absence of metals, low cost, environmental friendliness, green solvent, non-toxicity, ease of handling, and utilization of renewable energy sources like visible light are some of this method's primary advantages.

Unique structural features of the Mycobacterium ribosome.

Protein synthesis in all the living cells is mediated by a large protein-RNA complex called the ribosome. These macromolecular complexes can range from 2.5 (prokaryotes) to 4.2 MDa. (eukaryotes) in size and undergo various conformational transitions during protein synthesis to translate the genetic code into the nascent polypeptide chains. Recent advances in cryo-electron microscopy (cryo-EM) and image processing methods have provided numerous detailed structures of ribosomes from diverse sources and in different conformational states resolved to near-atomic resolutions. These structures have not only helped in better understanding of the translational mechanism but also revealed species-specific variations or adaptations in the ribosome structures. Structural investigations of the ribosomes from Mycobacterium smegmatis (Msm) and its closely related pathogenic Mycobacterium tuberculosis (Mtb) lead to the identification of two additional ribosomal proteins named as bS22 and bL37 and several unique extensions in ribosomal-protein and ribosomal-RNA. Hibernation Promoting Factor (HPF) bound structure of Msm ribosome, termed as the hibernating ribosome, possibly indicates a new mechanism of ribosome protection during dormancy. These studies enabled the identification of the mycobacteria-specific ribosomal features and provides an opportunity to understand their function and target them for further drug-discovery purposes. Here we review the unique structural features identified in Msm ribosome and their possible implications in comparison to a well-studied Escherichia coli (Ec) ribosome.