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A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding N-oxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2-Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high-to-quantitative yields utilizing 10 mol % of the catalyst and H2O2 as the oxidant. [ABSTRACT FROM AUTHOR]

Abstract: Among the various versions of the aldol reaction, the enantioselective reaction between cyclic ketones and aldehydes constitutes a typical reaction model for the evaluation of novel organocatalysts. A multifunctional organocatalyst consisting of a prolinamide moiety, a gem diamine unit and a urea group was successfully employed in this asymmetric transformation. The products of the reaction between various ketones and aldehydes were obtained in high yields (up to 98%) with excellent diastereo- (up to >98:2 dr) and enantioselectivities (up to 99% ee). [Copyright &y& Elsevier]

Abstract: Sulfonamides of the non-natural amino acid homoproline and the dipeptide Pro–Phe were synthesised and evaluated for their catalytic activity in Michael and aldol reactions. Sulfonamides of homoproline outperform proline and Pro–Phe in the Michael reaction, whereas sulfonamides of Pro–Phe lead to better results in the aldol reaction. The results of the present study show that the conversion of the carboxylic group of either homoproline or dipeptide Pro–Phe to the bioisosteric acyl sulfonamide group lead to improved organocatalysts. [Copyright &y& Elsevier]

Coupling of diphenylvinyl sulfonium triflate with nucleophiles and either aldehydes or imines gives epoxides and aziridines, respectively, in a three-component reaction. cis-Aziridines could be formed in good diastereomeric ratio, and the selectivity was correlated to the reactivity of the imine. This represents the first study of cis/trans selectivity in the reactions of imines with non�stabilized sulfur ylides. [ABSTRACT FROM AUTHOR]

Dihydrolevoclucosenone (Cyrene is its market name) is a biomass-derived solvent that can be produced in only two steps from biomass, while being biodegradable, non-mutagenic and non-toxic. Its "green" profile combined with its physical properties makes Cyrene a plausible substitute for a number of widely used toxic organic solvents. The first attempt to assess Cyrene as a solvent dates back to 2014 and since then, numerous research groups have opted for this promising alternative. Cyrene has successfully been employed as a solvent in materials chemistry, peptide chemistry, organic synthesis and many more research fields, which are going to be discussed in the context of this review. [ABSTRACT FROM AUTHOR]

A novel, mild, metal-free and easy-to-execute procedure for the C–H acetalization of O-heterocycles via visible light activation is presented, utilizing phenylglyoxylic acid as the photoinitiator. Biomass-derived O-heterocycles, like THF, can be employed, while primary, secondary alcohols and alcohols bearing a variety of functionalities were succesfully employed, affording the desired acetals in high yields. Facile acidic deprotection was also performed. [ABSTRACT FROM AUTHOR]

Michael addition represents a common organic transformation for the generation of C-C bonds in Organic Synthesis. Photochemistry is a branch of Organic Chemistry, which specializes in the acceleration of organic reactions utilizing light as the energy source. In our environmentally conscious world, the necessity of green chemistry processes has never been more apparent and herein, we introduce an environmentally benign photochemical protocol for the Michael addition of indoles to β-nitroolefins without the use of a photocatalyst, just by employing water as the solvent. A variety of substituted β-nitroolefins and indoles were converted into the desired products in good to high yields. [Display omitted] • A photochemical protocol for the Michael addition of indoles to β-nitroolefins is introduced. • Water is employed as the solvent and 390 nm irradiation is required to achieve excellent yields. • No external photocatalyst or catalyst is required. [ABSTRACT FROM AUTHOR]

The Michael‐type addition of indoles represents one of the most important C−C bonds forming reactions at their C‐3 position. Herein, we present a mild, versatile and sustainable protocol for the efficient preparation of β‐indolylketones via a Michael addition between indoles and chalcones or α,β‐unsaturated ketones in the presence of substituted arylazo sulfones as photoacid generators (PAGs). [ABSTRACT FROM AUTHOR]

Light‐mediated processes have received significant attention, since they have re‐surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ‐Lactones and cyclopropanes are prevalent moieties, found in numerous natural products and pharmaceuticals. Among various methods for their synthesis, light‐mediated protocols are coming to the spotlight, although these are contingent upon the use of photoorgano‐ or metal‐based catalysts. Herein, we introduce a novel photochemical activation of iodo‐reagents via the use of cheap sodium ascorbate or ascorbic acid to enable their homolytic scission and addition onto double bonds. The developed protocol was applied successfully to the formal [3+2] cycloaddition for the synthesis of γ‐lactones, traditional atom transfer radical addition (ATRA) reactions and the one‐pot two‐step conversion of alkenes to cyclopropanes. In all cases, the desired products were obtained in good to high yields, while the reaction mechanism was thoroughly investigated. Depending on the nature of the iodo‐reagent, a halogen or a hydrogen‐bonded complex is formed, which initiates the process. [ABSTRACT FROM AUTHOR]

The epoxidation of alkenes has altered and reshaped the way scientists think in modern organic synthesis. Herein, a novel, sustainable and eco‐friendly protocol for the epoxidation of alkenes is reported, utilizing hydrogen peroxide as the green oxidant and, for the first time, hydroxamic acid derivatives as the organocatalyst. The presented methodology is very effective, leading to good to high yields for the oxidation of a variety of olefins, while various functional groups are well tolerated. Mechanistic studies utilizing direct infusion high resolution mass spectrometry (DI‐HRMS) provide strong evidence for the mechanism of the organocatalytic oxidation. [ABSTRACT FROM AUTHOR]

This article discusses the use of boronic acids in the synthesis of phenols, which are important compounds found in natural products and pharmaceuticals. The researchers focus on developing environmentally friendly and sustainable methods for preparing phenols from boronic acids. They explore different photocatalysts and solvents to optimize the oxidation reaction. The study finds that anthraquinone is an effective photocatalyst and 2-Me-THF is the best solvent for the reaction. The researchers aim to provide a more sustainable protocol for the oxidation of boronic acids. Another study described in the document investigates the photochemical aerobic oxidation of boronic acids to phenols. The researchers tested different additives and found that N,N'-diisopropylethylamine (DIPEA) was the most suitable base, resulting in the complete formation of phenol. They also explored the range of substrates and found that various aryl-substituted boronic acids could be converted into the corresponding phenols with moderate to excellent yields. Mechanistic studies suggested a mixed pathway involving the generation of a superoxide anion and the formation of hydrogen peroxide. Overall, this study presents an environmentally friendly and efficient method for the oxidation of boronic acids. [Extracted from the article]

The Friedel–Crafts arylation is among the most known organic reactions, usually being promoted by a Lewis acid, that have been employed for the synthesis of bis-indolyl methanes. Herein, we report a mild, inexpensive, green and organocatalytic protocol for the promotion of a Friedel–Crafts-type reaction between indoles and aldehydes, where N-heterocyclic iod(az)olium salts are utilized as halogen-bonding catalysts, leading to the double addition of the indole motif. A variety of aliphatic and aromatic aldehydes were converted into diarylmethanes in good to high yields, while the scope of indoles was also investigated. Water was employed as the solvent, while the reaction time was short. The reaction mechanism was also studied. [ABSTRACT FROM AUTHOR]

The niche field of photochemistry offers opportunities that are not found in "traditional" ground state chemical pathways. Aminochlorinated derivatives are an interesting family of 1,2‐difunctionalised compounds that provide access to a variety of natural products and pharmaceutical active substances. A practical, catalyst‐free chloroamination protocol is described herein, providing access to intermediates of great importance, utilising mild and photochemical reaction conditions (370 nm), where N‐chlorosulfonamides are used as both nitrogen and chlorine sources. A wide variety of olefins, decorated with a plethora of functional groups, was tested providing excellent results (28 examples, 18–88 % yield). Mechanistic studies (UV‐Vis, control experiments and quantum yield measurement) were also performed. [ABSTRACT FROM AUTHOR]

In this study, 3H‐phenothiazin‐3‐one is identified as a photocatalyst for the photochemical oxidation of sulfides to sulfoxides. This photocatalytic method uses a low catalyst loading (0.05 mol%), molecular oxygen as the sole oxidant, and a blue LED lamp as the irradiation source. It can be applied to the oxidation of both alkyl‐aryl and alkyl‐alkyl sulfides. Moreover, the method is also applicable in the synthesis of the known pharmaceutically active compounds Modafinil and Sulforaphane. [ABSTRACT FROM AUTHOR]

In recent years, the development of light‐mediated methods for synthetic applications has attracted high interest, because such methods constitute alternative approaches for the production of valuable chemical products. We study herein a photochemical protocol for the synthesis of Weinreb amides and morpholine amides from carboxylic acids. Various carboxylic acids were directly coupled to N,O‐dimethylhydroxylamine, upon irradiation with either LED 370 nm or sunlight in the presence of 4‐dimethylaminopyridine and bromotrichloromethane, providing Weinreb amides in moderate to high yields. Similarly, morpholine amides were obtained in satisfactory to high yields under sunlight or LED 370 nm irradiation. Thus, the versatile building blocks Weinreb amides and morpholine amides may be efficiently synthesized directly from carboxylic acids by light‐mediated approaches, without the need of coupling reagents or pre‐activation of carboxylic acids. [ABSTRACT FROM AUTHOR]

The direct amide bond formation between a carboxylic acid and an amine still constitutes a challenging reaction for both academia and industry. We demonstrate herein that several pairs of amines (halogen bond acceptors) and organohalogen sources may be used for the photochemical amidation reaction under either UVA or sunlight irradiation. Our studies led to the identification of pyridine‐CBr4 as an efficient agent to perform amide synthesis under LED 370 nm irradiation, avoiding super‐stoichiometric quantities. An extended substrate scope was demonstrated, showing that the widely used amino and carboxyl protecting groups are compatible with this photochemical protocol, while a number of industrially interesting products and bioactive compounds were synthesized. Direct infusion‐high resolution mass spectrometry studies suggest an unprecedented type of carboxylic acid activation mode upon irradiation, involving the generation of a symmetric anhydride, an active ester with pyridine N‐oxide and a mixed anhydride with hypobromous acid. [ABSTRACT FROM AUTHOR]

Since the United Nations set goals dealing with climate change, the chemical industry has focused on recycling the already-used polymers, targeting the reinsertion of plastic waste to market via new products through reforming. Upcycling of polystyrene plastic waste is becoming one of the hottest fields of research in plastic upconversion. Herein, we introduce a novel, green, organocatalytic and photochemical aerobic upcycling process of polystyrene to benzoic acid, utilizing anthraquinone as the photocatalyst, LED 390 nm as the irradiation source and air as the sole oxidant. The developed protocol was applied successfully to the upcycling of daily-life used polystyrene products, leading to yields varying from 25% to 58%. Moreover, the obtained upcycled product from the polystyrene materials was employed to the successful synthesis of bioactive molecules, such as acetylsalicylic acid. [ABSTRACT FROM AUTHOR]

A novel and easy‐to‐execute light‐driven protocol for the preparation of alkyl boronic acid pinacol esters from vinyl boronate using N‐hydroxyphthalimide esters as the potential precursor is described. In this photochemical protocol, the N‐hydroxyphthalimide ester's fragmentation generates C‐centered radicals, which undergo a radical Michael addition to vinyl boronic pinacol ester furnishing the desired products. A good substrate scope having various functionalities is presented and good to high yields are obtained. [ABSTRACT FROM AUTHOR]

The development of light‐mediated methods for synthetic applications is increasingly attracting high interest. We present herein a new photochemical protocol for the synthesis of hydroxamic acids, which constitute an important class of medicinal agents, mainly due to their anticancer properties. The method is mediated by UVA‐light or sunlight and its key point is the generation of a charge transfer complex by the interaction of 4‐dimethylaminopyridine with a halomethane. Various carboxylic acids were directly coupled with O‐protected hydroxylamines, upon irradiation with either LED 370 nm or solar light. A detailed study of the mechanism was carried out by the employment of direct infusion–high resolution mass spectrometry (DI‐HRMS), providing experimental evidence for the formation of various activated species, which may lead to the desired product. The light‐mediated protocol was applied in the synthesis of the drugs Vorinostat and Bufexamac. [ABSTRACT FROM AUTHOR]

Thiiranes, the corresponding sulfur analogues of epoxides, are less studied and less encountered in literature. This might be due to the limited existing synthetic approaches for their synthesis. Herein, a mild, sustainable and efficient organocatalytic synthesis of thiiranes has been developed. Starting from olefins and utilizing the epoxidation protocol developed in the Kokotos' group, which employs 2,2,2‐trifluoroacetophenone as the organocatalyst and H2O2 as the oxidant, followed by ring opening by thiourea, a variety of thiiranes were synthesized. Both aromatic and aliphatic moieties are well tolerated, leading to thiiranes in moderate to excellent yields. [ABSTRACT FROM AUTHOR]

The development of green and sustainable methods for the conversion of aldehydes to carboxylic acids is of high academic and industrial interest. We demonstrate herein a practical and efficient light-promoted oxidation of aldehydes, utilising atmospheric oxygen as the sole oxidant. The transformation is promoted by either sunlight or LED 370 nm irradiation, without the use of a catalyst. A solvent mixture of acetone and water proved to be the most effective solvent medium. A wide range of aliphatic or aromatic aldehydes were successfully employed, providing the corresponding carboxylic acids in high to excellent yields. A mechanism was proposed based on direct infusion-high resolution mass spectrometry (DI-HRMS) studies, suggesting a solvent-assisted oxidative transformation. The method is green, sustainable and operationally simple under very mild conditions. [ABSTRACT FROM AUTHOR]

Correction for 'Organocatalytic Friedel–Crafts arylation of aldehydes with indoles utilizing N-heterocyclic iod(az)olium salts as halogen-bonding catalysts' by Eirini M. Galathri et al., Green Chem., 2023, https://doi.org/10.1039/D3GC03687A. [ABSTRACT FROM AUTHOR]