Synlett

A new protocol for accessing 3,4-dihydroquinolin-2(1H)-ones was established through a sequence of iron-catalyzed photoredox generation of carbamoyl radicals from oxamic acids, addition of the carbamoyl radicals to electron-deficient alkenes, intramolecular cyclization, and aromatization. The process is compatible with a variety of N-phenyloxamic acids and monosubstituted, 1,1-disubstituted, and trisubstituted electron-deficient alkenes. Employing cheap, readily available, and environmentally benign iron as the catalyst, the protocol provides an excellent alternative for synthesis of 3,4-dihydroquinolin-2(1H)-ones.

A simple, efficient, and environmentally benign method for the direct C-3-alkoxycarbonylation of 2H-indazoles using alkyl carbazates has been developed under metal-free conditions at room temperature. This current protocol represents a facile access to C-3-carboxylic ester derived 2H-indazoles with wide functional group tolerance in good to excellent yields. The mechanistic studies suggest that the reaction proceeds through a radical pathway.

A novel method was developed to synthesise chromene-lactone analogues of podophyllotoxin using an ultrasound-assisted multicomponent reaction (MCR). The MCR involved tetronic acid, phenols, and aromatic aldehydes and was promoted by BF3·OEt2, resulting in the production of ten derivatives with different substituents on the aromatic rings in yields ranging from 32% to 93%. These compounds are of interest due to their reported activity against tumour cells. Their ease of synthesis through the MCR may allow for more in-depth studies on anticancer activity, as well as investigations of other biological targets. The synthesised derivatives contain important pharmacophoric groups for potential applications in medicinal chemistry.

Here we describe a homocoupling reaction of arylboronic acid facilitated by silver carbonate, which proceeds smoothly in MeOH even at ambient temperature. The reaction exhibits broad functional group compatibility, affording a variety of symmetrical biaryls in satisfactory yields. Silver nanoparticles formed in situ serve as an accelerator in this process. Moreover, initial mechanistic investigations suggest that this transformation may occur via a radical mechanism.

Pyrazoloindolones are synthesized from N-tosylhydrazones in a one-pot multistep process which include base-promoted (i) electrocyclization reaction of N-tosylhydrazones derived from α,β-unsaturated aldehydes, (ii) aromatic nucleophilic substitution, and (iii) a domino cyclization–oxidation process under aerobic conditions.

The cleavage of double bonds in alkenes constitutes an integral process in converting feedstock materials into high-value synthetic intermediates. Well-known examples such as the oxidative cleavage of olefins and olefin metathesis only facilitate the synthesis of oxygen-containing compounds and the recombination of olefins. Therefore, it is appealing to extend C=C double bond cleavage to yield more abundant transformations. Herein, we report a novel photocatalytic approach for the deconstructive carboxylation of alkenes with CO2 for the synthesis of carboxylic acids in the absence of transition metals. Compared with reported carboxylations with CO2 during which carbon numbers are typically increased, we achieve the exchange of carbon dioxide with one of the carbons of the alkene double bond, thus providing carboxylic acids with unchanged carbon numbers when terminal alkenes are used.

An operationally simple method has been developed for the synthesis of N-alkylsulfonamides from benzylic alcohols and sulfonamides in the presence of molecular iodine and triethylsilane. Various benzylic alcohols and sulfonamides were evaluated, and iodides generated in situ were shown to be the key intermediates.

Synlett 2024; 35: V-DOI: 10.1055/s-0043-1774867Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2024; 35: A87-A102DOI: 10.1055/s-0043-1763985Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

The development of complex molecular scaffolds with defined folding properties represents a central challenge in chemical research. Proteins are natural scaffolds defined by a hierarchy of structural complexity and have evolved to manifest unique functional characteristics; for example, molecular recognition capabilities that facilitate the binding of target molecules with high affinity and selectivity. Utilizing these features, proteins have been used as a starting point for the design of synthetic foldamers and enhanced biocatalysts, as well as bioactive reagents in drug discovery. In this account, we describe the strategies used in our group to stabilize protein folds, ranging from the constraint of bioactive peptide conformations to chemical protein engineering. We discuss the evolution of peptides into peptidomimetics to inhibit protein–protein and protein–nucleic acid interactions, and the selective chemical modification of proteins to enhance their properties for biotechnological applications. The reported peptide- and proteomimetic structures cover a broad range of molecular sizes and they highlight the importance of structure stabilization for the design of functional biomimetics.1 Introduction2 Constraining the Conformation of Peptides3 Peptide-Based Covalent Protein Modifiers4 Chemical Protein Engineering5 Conclusions