Copper-Catalyzed Propargylation of Nitroalkanes

Photo-Driven Direct Construction of Imidazolidines from Anilines and Paraformaldehyde and Its Application in Polyoxymethylene Plastics Usage

Imidazolines play pivotal roles in numerous fields. However, the direct construction of imidazolines from primary amines involves precise C-C and C-N bond formations, rendering this area still underdeveloped to this day. Herein, a photo-driven metal-free catalytic system has been successfully applied to a novel coupling-cyclization reaction between arylamines and formaldehyde, enabling the direct synthesis of various 1,3-diarylimidazolines from primary amines. Notably, this method also facilitates the chemical conversion of polyoxymethylene plastics under these conditions. The present work provides new insights and directions for both imidazoline synthesis and plastic degradation.

Enamine Synthesis via Regiocontrolled 6-endo-dig and 5-exo-dig Tethered Carboamination of Propargylic Alcohols

Enamines are versatile building blocks for the synthesis of biologically active compounds. Nevertheless, only a limited number of strategies have been reported for preparing trisubstituted enamines in a regio- and stereoselective manner. Herein, we report a regiocontrolled 6-endo and 5-exo tethered carboamination of propargylic alcohols for the synthesis of trisubstituted enamines. High regioselectivity was achieved through fine-tuning of the amine protecting group during the Pd-catalyzed carboamination. The introduced trifluoromethylated tether enables further stereoselective functionalizations, such as hydrogenation and fluorination.

Three-Component cine,ipso-Disubstitution of Nitrocoumarins

The development of a three-component cine,ipso-disubstitution of nitrocoumarins is reported. The reaction leverages the electrophilicity of nitrocoumarins, the nucleophilicity of nitronates, and the leaving group ability of nitrite (NO2-) to yield complex polyfunctionalized biaryls that often display stable axial chirality.

Photoredox-Nickel Dual-Catalyzed C-Alkylation of Secondary Nitroalkanes: Access to Sterically Hindered α-Tertiary Amines

The preparation of tertiary nitroalkanes via the nickel-catalyzed alkylation of secondary nitroalkanes using aliphatic iodides is reported. Previously, catalytic access to this important class of nitroalkanes via alkylation has not been possible due to the inability of catalysts to overcome the steric demands of the products. However, we have now found that the use of a nickel catalyst in combination with a photoredox catalyst and light leads to much more active alkylation catalysts. These can now access tertiary nitroalkanes. The conditions are scalable as well as air and moisture tolerant. Importantly, reduction of the tertiary nitroalkane products allows rapid access to α-tertiary amines.

Asymmetric C-Alkylation of Nitroalkanes via Enzymatic Photoredox Catalysis

Tertiary nitroalkanes and the corresponding α-tertiary amines represent important motifs in bioactive molecules and natural products. The C-alkylation of secondary nitroalkanes with electrophiles is a straightforward strategy for constructing tertiary nitroalkanes; however, controlling the stereoselectivity of this type of reaction remains challenging. Here, we report a highly chemo- and stereoselective C-alkylation of nitroalkanes with alkyl halides catalyzed by an engineered flavin-dependent "ene"-reductase (ERED). Directed evolution of the old yellow enzyme from Geobacillus kaustophilus provided a triple mutant, GkOYE-G7, capable of synthesizing tertiary nitroalkanes in high yield and enantioselectivity. Mechanistic studies indicate that the excitation of an enzyme-templated charge-transfer complex formed between the substrates and cofactor is responsible for radical initiation. Moreover, a single-enzyme two-mechanism cascade reaction was developed to prepare tertiary nitroalkanes from simple nitroalkenes, highlighting the potential to use one enzyme for two mechanistically distinct reactions.