A visible light-initiated, one-pot, multi-component synthesis of 2-amino-4-(5-hydroxy-3-methyl-1H-pyrazol-4-yl)-4H-chromene-3-carbonitrile derivatives under solvent- and catalyst-free conditions

Visible-Light Photocatalysis for Sustainable Chromene Synthesis and Functionalization

Chromenes represent a biologically significant family of heterocycles, widely present in pharmaceutical compounds and secondary metabolites. Their importance in synthesis and medicinal chemistry has driven continuous efforts to develop advanced and efficient synthetic methodologies. Over the past decade, photoredox catalysis has revolutionized Organic Synthesis, offering innovative and sustainable strategies for the construction and functionalization of complex molecules. The synthesis of chromene derivatives has greatly benefited from the integration of visible-light-promoted methodologies, which utilize light as an abundant and non-toxic energy source, enabling greener chemical transformations. In this review, the latest progress in visible-light-mediated approaches for the synthesis of chromene derivatives, along with the photochemical reactivity of these relevant frameworks, are summarized.

Mechanochemical IMCR and IMCR-post transformation domino strategies: towards the sustainable DOS of dipeptide-like and heterocyclic peptidomimetics

A facile, rapid, sustainable one-pot Diversity Oriented Synthesis of peptidomimetics via mechanochemical IMCR-based domino strategies.

Eco-friendly synthesis of chromeno[4,3-b]chromenes with a new photosensitized WO3/ZnO@NH2-EY nanocatalyst

A new heterogeneous photoredox nanocatalyst WO₃/ZnO@NH₂-EY (EY: eosin Y) was fabricated and characterized employing some instrumental techniques such as XRD, FT-IR, ICP, TGA, and SEM. The photocatalytic efficiency of the prepared material was investigated in the preparation of various chromeno[4,3-b]chromenes via a simple and practical method. The chromene derivatives were prepared through the condensation of aromatic aldehydes, dimedone, and coumarin under an open-air atmosphere in the presence of a green LED under solventless conditions. The significant advantages of this new method include low reaction time, easy work-up, cost-effective, wide substrate scope, excellent yield, and complete atom economy of the final products. Moreover, the prepared photocatalyst could be frequently recovered up to four times with only a little decrease in the catalytic activity. Furthermore, the progress of the condensation reaction is demonstrated to occur via a radical mechanism, which shows that reactive species such as ˙O₂⁻ and OH˙ together with h⁺ would be involved in the photocatalytic process. Stability and reusability studies also warranty good reproducibility of the nanocatalyst for at least 4 runs. Eventually, a hot filtration test ensured that the nanohybrid catalyst is stable in the reaction medium and its catalytic activity originates from the whole undecomposed conjugated composite.

WO₃/ZnO@NH₂-EY is disclosed in the preparation of chromenes under air in the presence of a green LED. ˙O₂⁻, OH˙, and h⁺ are proposed as reactive species and hot filtration test assured stability and reusability of the nanocatalyst.

Nucleophilic Acylation with Aromatic Aldehydes to 2 Bromoacetonitrile: An Umpolung Strategy for the Synthesis of Active Methylene Compounds

BACKGROUND

A novel one-pot N-heterocyclic carbene (NHC)-catalysed acylation of 2- bromoacetonitrile with aromatic aldehydes is reported. The protocol involves carbonyl umpolung reactivity of aldehydes in which the carbonyl carbon attacks nucleophilically (as d1 nucleophile) on the electrophilic terminal of 2-bromoacetonitrile to afford 3-aryl-3-oxopropanenitrile. The salient features of this procedure are short reaction time, operational simplicity, ambient temperature, no by-product formation and high yields.

MATERIALS AND METHODS

A flame-dried round bottom flask was charged with Imidazolium salts (3a) (0.20 mmol). Aldehyde 1a (1.0 mmol), 2-bromoacetonitrile 2 (1.0 mmol), and THF / t-BuOH 5 mL; 10:1) were added at positive nitrogen pressure followed by the addition of DBU (0.15 mmol) through stirring. The resulting yellow- orange solution was stirred at room temperature for 5-6 h. After completion of the reaction (TLC monitored), the reaction mixture was concentrated under reduced pressure. The product was purified using hexane / EtOAc (10:1) as an eluent to provide analytically pure compound 4a. Physical data of representative compounds and the NMR spectroscopic data are in agreement with the literature value.

RESULTS AND DISCUSSION

The salient features of this procedure are short reaction time, operational simplicity, ambient temperature, no by-product formation and high yields.

CONCLUSION

To sum up, we have developed a convenient, efficient and one-pot route for 3-oxo-3- phenylpropanenitrile synthesis from NHC promoted direct nucleophilic acylation of aromatic aldehydes using 2- bromoacetonitrile. This method provided a wide range of products and good yields. To best of our knowledge, this is the new report for the synthesis of 3-oxo-3-phenylpropanenitrile through NHC promoted nucleophilic acylation of aromatic aldehyde.

Homophtalonitrile for Multicomponent Reactions: Syntheses and Optical Properties of o-Cyanophenyl- or Indol-3-yl-Substituted Chromeno[2,3-c]isoquinolin-5-Amines

Malononitrile is a useful reagent for multicomponent reactions with hundreds of methods developed. In this paper, we suggest α‐(cyano)‐o‐tolunitrile (homophtalonitrile) to work as a vinylogous malononitrile. Thus, a organocatalytic pseudo‐three‐component reaction of homopthalonitrile (2 equiv) and o‐hydroxybenzaldehyde, leading to the diastereoselective formation of 5‐amino‐12H‐chromeno[2,3‐c]isoquinolin‐12‐yl)(cyano)methyl)benzonitriles, was discovered. The possibility to employ other nucleophiles was demonstrated for indoles, and a sequential three‐component reaction of homophtalonitrile, o‐hydroxybenzaldehyde, and (aza)indole, giving 12‐(1H‐Indol‐3‐yl)‐12H‐chromeno[2,3‐c]isoquinolin‐5‐amines, was developed. The photophysical properties of the synthesized compounds have been studied, revealing high fluorescence quantum yields (42–70 %) for indol‐3‐yl substituted 12H‐chromeno[2,3‐c]isoquinolin‐5‐amines and reversible fluorescence quenching under acidic conditions.