LongLarf

This article highlights the recent seminal findings on the possibility to use photoexcited nitroarenes as modular and easily dosable reagents which can mimic the reactivity of ozonolysis for the oxidative conversion of alkenyl bonds into carbonyl groups in a highly selective fashion.

Abstract

Oxidative cleavage of alkenes into carbonyl molecules mainly relies on either ozonolysis or Lemieux-Johnson oxidation involving high valent transition metal oxides. Safety, technical concerns and highly oxidizing conditions of both these procedures limited their adoption in streamlined synthesis. Like ozone, photosensitized nitroarenes can deliver similar types of [3+2] cycloaddition products with alkenes through biradical formation and the resulting “N-doped” ozonides can safely be converted to the corresponding carbonyl compounds through hydrolysis. The high prevalence of nitroarenes with diverse electronic and steric profiles combined with the mild oxidizing power allow to modulate site-selectivity and tolerate highly sensitive functional groups ideal for application in complex molecular setup.

Nature, Published online: 05 October 2022; doi:10.1038/s41586-022-05278-9

NMR spectroscopy has been used to guide the directed evolution of myoglobin to a Kemp eliminase with high catalytic efficiency, outlining an approach that is likely to be generally applicable to other enzyme activities.

Nature Chemistry, Published online: 10 October 2022; doi:10.1038/s41557-022-01057-1

Technologies for profiling biological environments with high spatiotemporal resolution are in demand to enable the discovery of new targets for addressing unmet clinical needs. Now, a deep red light-mediated photocatalytic strategy for the targeted activation of aryl azides has been developed. This platform enables mapping of protein microenvironments in physiologically relevant systems.

Abstract

Organocatalyzed Michael addition of N-substituted tetramic acids to nitroalkene acceptors followed by O-alkylation gave polyfunctionalized tetramic acid (31 examples, 59–94% ee). The enantioselectivity of the product was influenced by the N-substituent of the substrate. Quantum chemical methods provided the mechanistic insights of the studied transformation. The preferred reaction pathway follows the model proposed by Pápai et al. Single crystal structure confirmed the absolute configuration, which was in line with the ECD measured and calculated structure. Additionally, a comparative study of the alkylation of a selected tetramic and tetronic acid with trans-β-nitrostyrene is disclosed. Follow-up amidations demonstrated the applicability of this class of compounds for the incorporation into both dipeptide and depsipeptide sequences.

Abstract

A copper-catalyzed cascade reaction for selective aerobic oxidative C−C bond cleavage of β-alkyl nitroolefins and subsequent oxidative amidation with amines or amides was reported. The reaction all exhibited high selectivities and gave the corresponding α-ketoamides with 66–88% yields. The mechanistic study revealed that the NO₂-directed aerobic oxidative C−C bond cleavage occurred on more electron-rich allylic nitro tautomers, which originated from the equilibrium of conjugated nitroalkenes.

Abstract

An organocatalyzed one-pot sequential deracemization of aromatic ketones bearing a stereogenic center at the α-position was achieved thanks to an acid-base strategy involving an enantioselective protonation reaction as a key step. This simple and efficient protocol yields enantioenriched ketones in up to 89% ee without the need to isolate sensitive intermediates such as silyl enolates. The key role of water in this process was underlined. This one-pot sequence constitutes a useful extension to previously reported chemically driven red-ox protocols, thus increasing the panel of molecules eligible to a deracemization strategy.

The combination of photochemistry with enzyme catalysis offers exciting opportunities to induce new reactivities and to create novel enzymes for reactions other than their native ones. Recently, Hyster and co-workers demonstrated this for a photoenzymatic asymmetric Csp ³−Csp ³ cross-electrophile coupling, a reactivity previously unknown to enzymes.

Abstract

Enzymes have several advantages over conventional catalysts for organic synthesis. Over the last two decades, much effort has been made to further extend the scope of biocatalytic reactions available to synthetic chemists, particularly by expanding the repertoire of enzymes for abiological transformations. In this regard, exciting new developments in the area of photobiocatalysis enable now the introduction of non-natural reactivity in enzymes to solve long-standing synthetic challenges. A recently described example from the Hyster group demonstrates in an unprecedented way how the combination of photochemistry with enzyme catalysis empowers the catalytic asymmetric construction of Csp ³−Csp ³ bonds with high chemo- and enantioselectivity.

Publication date: 8 December 2022

Source: Chem, Volume 8, Issue 12

Author(s): Jia Qiu, Jiancong Xie, Shimin Su, Yadong Gao, Han Meng, Yuedong Yang, Kuangbiao Liao

Publication date: 9 February 2023

Source: Chem, Volume 9, Issue 2

Author(s): Cong Guo, Li-Qun Zhang, Wenjun Jiang

Nature, Published online: 21 September 2022; doi:10.1038/s41586-022-05342-4

Enantioselective [2+2]-cycloadditions with triplet photoenzymes

Nature, Published online: 21 September 2022; doi:10.1038/s41586-022-05335-3

A Designed Photoenzyme for Enantioselective [2+2]-Cycloadditions

Nature Catalysis, Published online: 20 September 2022; doi:10.1038/s41929-022-00839-7

Single-atom, small cluster and nanoparticle catalysts feature intriguing reactivity for a variety of transformations, which is often attributed to the properties of specific atomic species. This Review critically revisits the reactivity of such catalysts in term of the ensemble effects that arise from the interaction of multiple metal atoms or single atomic species with neighbouring atoms from supports, additives or surface ligands.

Science, Volume 377, Issue 6612, Page 1323-1328, September 2022.