Direct Access to Unnatural Cyclobutane α-Amino Acids through Visible Light Catalyzed [2+2]-Cycloaddition.

In this work, we report the first selective, photocatalyzed [2+2]-cycloaddition of dehydroamino acids with styrene-type olefins. This simple, mild, and scalable approach relies on the use of the triplet energy transfer catalyst [Ir(dFCFppy)dtbpy]PF under visible light irradiation and provides fast access to value-added substituted strained cyclobutane α-amino acid derivatives.

Easy access to drug building-blocks through benzylic C-H functionalization of phenolic ethers by photoredox catalysis.

A visible light-mediated photocatalyzed C-C-bond forming method for the benzylic C-H functionalization of phenolether containing synthetic building blocks based on a radical-cation/deprotonation strategy is reported. This method allows the mild, selective generation of benzyl radicals in phenolic complex molecules and drug-like compounds, providing new entries in synthetic and medicinal chemistry.

Direct C-H Bond Imidation with Benzoyl Peroxide as a Mild Oxidant and a Reagent.

A simple and mild Cu-catalyzed oxidative three-component oxidative Ugi-type method for the synthesis of a variety of substituted imides has been developed. In this direct imidation approach, benzoyl peroxide serves as both the oxidant and the carboxylate source, allowing not only the functionalization of C(sp)-H bonds in α-position to an amine but also benzylic substrates. This procedure presents a wide substrate-type and functional group tolerance.

Double Cu-Catalyzed Direct Csp -H Azidation/CuAAC Reaction: A Direct Approach towards Demanding Triazole Conjugates.

The first one-pot procedure for the double copper(I)-catalyzed oxidative Csp -H azidation-CuAAC process, implying unstable azide intermediates and easy-to-remove reagents under water-tolerant conditions, is presented. The combination of tert-butyl hydroperoxide as oxidant and TMSN as azide source for the C-H bond azidation, which produces harmless side-products such as tBuOH and H O, probed to be perfectly compatible with the following cycloaddition step. Highly demanding 1,2,3-triazoles could be then directly obtained in good overall yields by extraction or simple crystallization, thus avoiding chromatography purifications.

Recent progress in mild Csp-H bond dehydrogenative or (mono-) oxidative functionalization.

Over the past few years, the development of oxidative methodologies towards efficient and selective direct Csp-H bond functionalization processes has attracted tremendous attention from synthetic chemists. However, only a little attention has been given to the key role of the nature of the oxidant. This review aims at providing a brief summary of the recent advances in mild and more benign oxidative Csp-H bond functionalization reactions, which are classified according to the type of oxidation system employed.