Exploration of Dimethylzinc-Mediated Radical Reactions

Et2Zn-Mediated Radical (3 + 2) Cycloaddition of Vinyl Azides with Ethyl Iododifluoroacetate to Access 3,3-Difluoro-γ-lactams

A diethylzinc-mediated radical (3 + 2) cycloaddition of vinyl azides with ethyl iododifluoroacetate is presented. The developed reaction features good functional group tolerance, broad substrate scope, and operational simplicity, enabling efficient assembly of a wide range of 3,3-difluoro-γ-lactam derivatives bearing an O-substituted quaternary carbon center in moderate to good yields. The utility of the method is showcased by a scaled-up reaction, conversion of the product, and late-stage structural modifications of a variety of pharmaceutical compounds.

Towards deeper understanding of multifaceted chemistry of magnesium alkylperoxides

Despite considerable progress in the multifaceted chemistry of non-redox-metal alkylperoxides, the knowledge about magnesium alkylperoxides is in its infancy and only started to gain momentum. Harnessing the well-defined dimeric magnesium tert-butylperoxide [(^f5BDI)Mg(μ-η²:η¹-OOtBu)]₂ incorporating a fluorinated β-diketiminate ligand, herein, we demonstrate its transformation at ambient temperature to a spiro-type, tetranuclear magnesium alkylperoxide [(^f5BDI)₂Mg₄(μ-OOtBu)₆]. The latter compound was characterized by single-crystal X-ray diffraction and its molecular structure can formally be considered as a homoleptic magnesium tert-butylperoxide [Mg(µ-OOtBu)₂]₂ terminated by two monomeric magnesium tert-butylperoxides. The formation of the tetranuclear magnesium alkylperoxide not only contradicts the notion of the high instability of magnesium alkylperoxides, but also highlights that there is much to be clarified with respect to the solution behaviour of these species. Finally, we probed the reactivity of the dimeric alkylperoxide in model oxygen transfer reactions like the commonly invoked metathesis reaction with the parent alkylmagnesium and the catalytic epoxidation of trans-chalcone with tert-butylhydroperoxide as an oxidant. The results showed that the investigated system is among the most active known catalysts for the epoxidation of enones.

Synthesis of amino-diamondoid pharmacophores via photocatalytic C-H aminoalkylation

We report a direct C-H aminoalkylation reaction using two light-activated H-atom transfer catalyst systems that enable the introduction of protected amines to native adamantane scaffolds with C-C bond formation. The scope of adamantane and imine reaction partners is broad and deprotection provides versatile amine and amino acid building blocks. Using readily available chiral imines, the enantioselective synthesis of the saxagliptin core and rimantadine derivatives is also described.

Radical Addition to N-Tosylimines via C-H Activation Induced by Decatungstate Photocatalyst

A method for the radical addition toward N-tosylimines based on light promoted C-H activation by tetrabutylammonium decatungstate is described. The reaction proceeds under irradiation using 400 nm light emitting diodes in conventional glassware. The method can be applied for alkylations (cycloalkanes, ethers, dimethylformamide) and acylation (primary aliphatic aldehydes) of both aromatic and aliphatic N-tosylimines.

1,2-Addition of Diethylzinc to a Bis(Imidazolyl)ketone Ligand

In this study, the selective 1,2-addition of diethylzinc to the ketone functionality of BMdiPhIK [bis(1-methyl-4,5-diphenylimidazolyl)ketone] is shown. The reaction product is isolated in a dimeric form with a planar Zn2(µ-O)2-motif keeping the two monomers together. This compound can serve as a model for reactive intermediates in the catalytic alkylation of ketones with diorganozinc reagents. Hydrolysis of this binuclear zinc compound leads to isolation of the C-alkylated product in 89 % yield. A reaction pathway is proposed in which BMdiPhIK initially coordinates to diethylzinc as a bidentate bis(nitrogen) ligand. This is followed by the homolytic cleavage of the Zn-Et bond and in-cage recombination of the Et-radical and the Zn-coordinated ligand-centered radical, which is mainly localized on the carbonyl moiety of the ligand.

An autocatalytic cycle in autoxidation of triethylborane

An autocatalytic cycle was found in the mechanism of autoxidation of triethylborane using density functional theory calculations, and studied in detail with kinetic simulations.