Heterogeneous Catalysis to Drive the Waste-to-Pharma Concept: From Furanics to Active Pharmaceutical Ingredients

A perspective on the use of heterogeneous catalysis to drive the waste-to-pharma concept is provided in this contribution based on the conversion of furanics to active pharmaceutical ingredients (APIs). The provided overview of the concept in this perspective article has been exemplified for two key molecule examples: Ancarolol and Furosemide

Cytosine Palladium Complex Supported on Ordered Mesoporous Silica as Highly Efficient and Reusable Nanocatalyst for One-Pot Oxidative Esterification of Aldehydes

The synthesis of esters is one of the most fundamental and significant subjects in organic chemistry and chemical industry because they are used in high-value products such as cosmetics, biofuel, pharmaceuticals, surfactants, and food ingredients. In this study, an efficient, economic, sustainable, and green protocol for oxidative esterification reaction has been developed. A one-pot direct transformation of aliphatic, aromatic, and unsaturated aldehydes into esters in the presence of oxygen has been carried out over mesoporous organosilica-supported palladium nanocatalyst (Pd-Cyt@SBA-15) under ambient conditions. Pd-Cyt@SBA-15 efficiently catalyzed selectively large-scale conversion of aldehydes into esters in high yields and large turnover numbers (TON = 98,000). Pd-Cyt@SBA-15 nanocatalyst demonstrated excellent reusability and stability and could be recycled up to ten times without loss of significant reactivity. ICP-AES analysis showed that no leaching of active palladium species occurred during the recycling process of the heterogeneous Pd-Cyt@SBA-15 nanocatalyst

8H-Chromeno[2′,3′:4,5]imidazo[2,1-a]isoquinoline

The title compound, C18H12N2O, comprises two aromatic fragments, viz., imidazo[2,1-a]isoquinoline and benzene, linked by oxygen and methyl­ene bridges. Despite the absence of a common conjugative system within the mol­ecule, it adopts an essentially planar conformation with an r.m.s. deviation of 0. 036 Å. In the crystal, due to this structure, mol­ecules form stacks along the b axis by π⋯π stacking inter­actions, with shortest C⋯C distances in the range 3.340 (4)–3.510 (4) Å. The mol­ecules are bound by inter­molecular C—H⋯O inter­actions within the stacks and C—H⋯π inter­actions between the stacks

Post-Ugi Cyclization for the Construction of Diverse Heterocyclic Compounds: Recent Updates

Multicomponent reactions (MCRs) have proved as a valuable tool for organic and medicinal chemist because of their ability to introduce a large degree of chemical diversity in the product in a single step and with high atom economy. One of the dominant MCRs is the Ugi reaction, which involves the condensation of an aldehyde (or ketone), an amine, an isonitrile, and a carboxylic acid to afford an α-acylamino carboxamide adduct. The desired Ugi-adducts may be constructed by careful selection of the building blocks, opening the door for desired post-Ugi modifications. In recent times, the post-Ugi transformation has proved an important synthetic protocol to provide a variety of heterocyclic compounds with diverse biological properties. In this review, we have discussed the significant advancements reported in the recent literature with the emphasis to highlight the concepts and synthetic applications of the derived products along with critical mechanistic aspects

Three-Component Reaction of 3-Arylidene-3H-Indolium Salts, Isocyanides, and Alcohols

A novel isocyanide-based multicomponent synthesis of alkyl aryl(indol-3-yl)acetimidates has been established. Starting from aryl(indol-3-yl)methylium tetrafluoroborates, aromatic isocyanides and alcohols, the imidates were obtained in moderate to very good yields. Consecutive four-component synthesis of the above mentioned imidates from N-alkylindoles, aromatic aldehydes, aromatic isocyanides and alcohols was also proposed. In addition, it was shown that in the presence of water, aryl(indol-3-yl)methylium tetrafluoroborates reacted with isocyanides to furnish aryl(indol-3-yl)acetamides

Methyl (2E)-3-[3-Benzyl-2-(3-methoxy-3-oxoprop-1-yn-1-yl)-2-(1-naphthyl)imidazolidin-1-yl]acrylate

Compounds with propargylamine moiety are useful synthetic precursors of several important classes of nitrogen-containing heterocycles. The title compound, methyl (2E)-3-[3-benzyl-2-(3-methoxy-3-oxoprop-1-yn-1-yl)-2-(1-naphthyl)imidazolidine-1-yl]acrylate, has been prepared by domino-reaction, employing easily available 1-benzyl-2-(1-naphthyl)-4,5-dihydro-1H-imidazole and methyl propiolate in a high 92% yield. The structure of title compound was determined using 1H-NMR, 13C-NMR, UV, FT-IR and HRMS (High-Resolution Mass Spectrometry)

1-Methyl-3-(2-oxo-2H-chromen-3-yl)-1H-imidazol-3-ium picrate

The title salt, C13H11N2O2+·C6H2N3O7−, is the unexpected product of a domino reaction of 3-cyanomethyl-1-methylimidazolium chloride with salicylic aldehyde in the presence of picric acid. In the cation, the 1H-imidazole ring is twisted by 63.2 (1)° from the 2H-chromen plane. In the crystal, cations and anions are alternately stacked along the a axis through π–π stacking interactions between the almost parallel aromatic rings [centroid–centroid distances = 3.458 (2) and 3.678 (2) Å]. The stacks are further linked by C—H...O hydrogen bonds into a two-tier layer parallel to (001)

Recent advances in spirocyclization of indole derivatives

Spiroindolines and spiroindoles are an important class of spirocyclic compounds present in a wide range of pharmaceuticals and biologically important natural alkaloids. Various spiroindolines and spiroindoles possess versatile reactivity which enables them to act as precursors for other privileged heterocycles. In view of the importance of this scaffold, many researchers focused their efforts to develop facile and mild synthetic methods for spirocyclization of indoles. However, the synthesis of spiroindolines and spiroindoles is known to be difficult due to rapid 1,2-migration to restore aromaticity. This review aims to briefly discuss the latest developments to access highly functionalized spiroindolines and spiroindoles to stimulate further research in the field to find new and efficient methodologies for accessing new spiroindolines and spiroindoles.status: publishe

Gold and silver nanoparticle-catalyzed synthesis of heterocyclic compounds

© 2018, Springer Science+Business Media, LLC, part of Springer Nature. [Figure not available: see fulltext.] In recent years, metallic nanoparticles have been a constant subject of attention for researchers. The transition of metal from microparticles to nanoparticles leads to a substantial change in its physical and chemical properties. Nanoparticles as catalyst in organic reactions provide additional benefits such as catalyst recycling, scale-up of reactions using continuous flow processes, and easy purification of the reaction mixture offering green and cost-effective alternatives. This review highlights some of the significant gold and silver nanoparticle-catalyzed reactions for the synthesis of various heterocyclic compounds. A brief synthetic methodology for different heterocyclic compounds is discussed along with the scope of the reaction.status: publishe

Visible light-mediated chemistry of indoles and related heterocycles

The use of visible light and photoredox catalysis emerged as a powerful and sustainable tool for organic synthesis, showing the high value of distinctly different ways of bond creation. Indoles and related heterocycles are widely-present in natural products, biologically active compounds, drugs, and agrochemicals. This review summarises the impact of visible light-promoted chemistry on the functionalization of indoles and on the synthesis and modification of indolines, indolin-2-ones, indolin-3-ones, and isatins. Almost 100 references starting from 2012 are cited.status: publishe