Microwave-assisted nanocatalysis: A CuO NPs/rGO composite as an efficient and recyclable catalyst for the Petasis-borono-Mannich reaction

Synergistic atom co-sharing and S-scheme heterojunction: constructing Cu/CuO/Cu2O with ultrathin graphene-like carbon derived from basil seeds for enhanced photo-oxidation of benzyl alcohols to aldehydes

This study is centered on the oxidative transformation of alcohols into their respective aldehyde compounds, employing an S-scheme heterostructure featuring CuO/Cu2O on graphene-like carbon (GLC) derived from a basil seed hydrogel. Experimental characterization and theoretical calculations highlight that the implementation of S-scheme heterostructures achieves not only enhanced charge-separation efficiency, facilitated by the interfacial built-in electric field, Cu co-sharing at the CuO/Cu2O interface, and electron carrier activity of the GLC support, but also maintains a strong driving force for photocatalytic organic conversion. The resulting nanocomposites play a crucial role in transferring and reducing the recombination of photoexcited charge carriers, preserving the oxidizability of CuO holes and the reducibility of Cu2O electrons. Through meticulous adjustment of precursor amounts, the CuO-Cu2O/GLC heterojunction exhibited the highest photocurrent at 6.83 mA cm-2, demonstrating optimal performance in the photocatalytic selective oxidation of benzyl alcohol with an average conversion rate of 95.0%. Furthermore, the stability of CuO-Cu2O/GLC was thoroughly investigated, revealing sustained high conversion even after five repeated experiments, underscoring its potential for practical applications. The study also proposes a plausible mechanism for the transformation of benzyl alcohol into benzaldehyde through capture experiments of active species. Importantly, this research introduces a straightforward in situ hydrothermal growth protocol for efficiently constructing metal oxide heterostructures wrapped in an rGO support. It provides valuable insights into designing new synthetic strategies for preparing efficient photocatalysts and hints at the development of novel, efficient, and practical photocatalytic systems.

Oxidation of Alcohols into Carbonyl Compounds Using a CuO@GO Nano Catalyst in Oxygen Atmospheres

In this article, the oxidation of alcohols into carbonyl compounds was studied in oxygen atmospheres using a copper oxide on graphene oxide (CuO@GO) nano composites catalyst, synthesized by the wet chemistry method. CuO@GO nano composites were prepared from GO, and CuO NPs by the sol-gel method. The transformation of aromatic alcohols into corresponding carbonyl compounds in good-to-high yields were observed using the CuO@GO catalyst under an oxygen atmosphere. Synthesized CuO@GO was confirmed by FT-IR, XRD, XPS, TEM, FE-SEM, TEM, and SEM analyses, and revealed intercalation of CuO-NPs on/in GO nano sheets through the chelation of Cu+2 ions with CO, COOH, and OH groups presenting on the GO nano sheets. The catalytic activity of CuO@GO nano composites for the conversion of alcohols into carbonyl compounds were evaluated through TOF (2.56 × 10−3 mol g−1 min−1). The use of CuO@GO has shown catalytic activity and recyclability with a high conversion of alcohols to ketones. We assume that the proposed CuO@GO catalyst can be used for other key organic transformations and will be evaluated in the future.

Site-specific role of bifunctional graphitic carbon nitride catalyst for the sustainable synthesis of 3,3-spirocyclic oxindoles in aqueous media

Functionalized graphitic carbon nitride (Sg-C₃N₄) has been manufactured and used as a reusable catalyst for the one-pot production of various spiro-pyrano chromenes and spiro indole-3,1′-naphthalene tetracyclic systems in aqueous media. An ultrasound-assisted method has been used for the functionalization of g-C₃N₄. The catalytic functionalities and the structural integrity of the catalyst were characterized via different analytical tools. The catalytic site-specific role of Sg-C₃N₄ was confirmed via various control experiments in one-pot reaction sequences. We recognized that Sg-C₃N₄ acts as a bifunctional acid–base catalyst for the first reaction sequence whereas it is an acidic catalyst for the second reaction sequence during the one-pot production of various spiro-pyrano chromenes. In addition, the bifunctional acid–base catalytic role of Sg-C₃N₄ has been confirmed for the first reaction sequence whereas it has a basic catalytic role for the second reaction sequence during the one-pot production of spiro indole-3,1′-naphthalene tetracyclic systems. Diverse C–C, C–O, and C–N bonds, six-membered cycles, stereogenic centers, and spiro frameworks were formed in a single reaction, enhancing the biocidal profile and possibly resulting in the discovery of new medicinal properties. The mild reaction environment, simple workup, easy separation, low cost, heterogeneity, and recyclability of Sg-C₃N₄ are some rewards of this approach.

Functionalized graphitic carbon nitride (Sg-C₃N₄) has been manufactured and used as a reusable catalyst for the one-pot production of various spiro-pyrano chromenes and spiro indole-3,1′-naphthalene tetracyclic systems in aqueous media.

Catalyst-free Synthesis of Aminomethylphenol Derivatives in Cyclopentyl Methyl Ether via Petasis Borono-Mannich Reaction

OBJECTIVE

Aminomethylphenol molecules have wider applications in pharmaceuticals, agrochemicals, plant protection and promising functional materials. The development of an efficient and practical method to prepare this class of compound is highly desirable from both environmental and economical points of view.

MATERIALS AND METHODS

In order to establish an effective synthetic method for preparing aminomethylphenol derivatives, the Petasis borono-Mannich reaction of salicylaldehyde, phenylboronic acid and 1,2,3,4- tetrahydroisoquinoline was selected as a model reaction. A variety of reaction conditions are investigated, including solvent and temperature. The generality and limitation of the established method were also evaluated.

RESULTS AND DISCUSSION

It was found that model reaction can be carried out in cyclopentyl methyl ether at 80 oC under catalyst-free conditions. This protocol, with broad substrate applicability, the reaction of various arylboronic acid, secondary amine and salicylaldehyde proceeded smoothly under optimal reaction conditions to afford various aminomethylphenol derivatives in high yields. A practical, scalable, and high-yielding synthesis of aminomethylphenol derivatives was successfully accomplished.

CONCLUSION

A catalyst-free practical method for the synthesis of minomethylphenol derivatives based on Petasis borono-Mannich (PBM) reaction of various arylboronic acid, secondary amine and salicylaldehyde in cyclopentyl methyl ether has been developed. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvents, use of cyclopentyl methyl ether as the reaction medium, clean reaction profiles, easy operation, and high to excellent yield.

The graphite-catalyzed ipso-functionalization of arylboronic acids in an aqueous medium: metal-free access to phenols, anilines, nitroarenes, and haloarenes

An efficient, metal-free, and sustainable strategy has been described for the ipso-functionalization of phenylboronic acids using air as an oxidant in an aqueous medium. A range of carbon materials has been tested as carbocatalysts. To our surprise, graphite was found to be the best catalyst in terms of the turnover frequency. A broad range of valuable substituted aromatic compounds, i.e., phenols, anilines, nitroarenes, and haloarenes, has been prepared via the functionalization of the C-B bond into C-N, C-O, and many other C-X bonds. The vital role of the aromatic π-conjugation system of graphite in this protocol has been established and was observed via numerous analytic techniques. The heterogeneous nature of graphite facilitates the high recyclability of the carbocatalyst. This effective and easy system provides a multipurpose approach for the production of valuable substituted aromatic compounds without using any metals, ligands, bases, or harsh oxidants.

Design, synthesis, and catalytic performance of modified graphene oxide based on a cobalt complex as a heterogenous catalyst for the preparation of aminonaphthoquinone derivatives

We are reporting a functionalized graphene oxide catalyst developed by modifying graphene oxide surface using the covalent attachment of an amino-functionalized SiO2 sphere/cobalt complex. Silica network has special characteristics including mechanical strength, high thermal and chemical stability with good dispersion in solvents. The silica/graphene oxide mixture provides improved properties and extends the scope of application. Graphene oxide was functionalized by spherical silica with the help of hybrid silane-containing nitrogen to coordinate with Co(ii) for increasing the catalytic activity. The catalyst was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), Energy Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Raman spectroscopy, and Thermal Gravimetric (TGA) analyses. The catalyst showed high catalytic activity for multi-component reactions in the synthesis of aminonaphthoquinones in ethanol solvent. The catalyst's ability to improve the yield (96-98%), reduce the reaction time (5-8 min), and recycling ability are important benefits for the catalyst.

Regioselective condensation of hydroxyaromatic compounds with 2,5-dimethoxytetrahydrofuran: facile one-pot synthesis of new substituted diaryl-fused 2,8-dioxabicyclo[3.3.2]nonanes comprising central ketal moieties

Regioselective synthesis of a series of novel diaryl- and naphthyl-fused 2,8-dioxabicyclo[3.3.2]nonanes was accomplished by a one-pot reaction of p-substituted phenols and 2-naphthol with 2,5-dimethoxytetrahydrofuran.

Reactivity and Synthetic Applications of Multicomponent Petasis Reactions

The Petasis boron-Mannich reaction, simply referred to as the Petasis reaction, is a powerful multicomponent coupling reaction of a boronic acid, an amine, and a carbonyl derivative. Highly functionalized amines with multiple stereogenic centers can be efficiently accessed via the Petasis reaction with high levels of both diastereoselectivity and enantioselectivity. By drawing attention to examples reported in the past 8 years, this Review demonstrates the breadth of the reactivity and synthetic applications of Petasis reactions in several frontiers: the expansion of the substrate scope in the classic three-component process; nonclassic Petasis reactions with additional components; Petasis-type reactions with noncanonical substrates, mechanism, and products; new asymmetric versions assisted by chiral catalysts; combinations with a secondary or tertiary transformation in a cascade- or sequence-specific manner to access structurally complex, natural-product-like heterocycles; and the synthesis of polyhydroxy alkaloids and biologically interesting molecules.