Convenient synthesis of α-amino amides using low-valent tantalum prepared from TaCl5 and Zn

Visible Light-Driven Flexible Synthesis of α-Alkylated Glycine Derivatives Catalyzed by Reusable Covalent Organic Frameworks

Herein, we report a heterogeneous visible light-driven preparation of α-alkylated glycine derivatives. This approach employed a β-ketoenamine-linked covalent organic framework (2D-COF-4) as the heterogeneous photocatalyst and N-hydroxy phthalimide (NHPI) esters as the alkyl radical sources. Numerous glycine derivatives, including dipeptides, were precisely and efficiently alkylated under visible light-driven reaction conditions. Based on the excellent photoactivity and organic reaction compatibility of 2D-COF-4, this alkylation could proceed flexibly in a green solvent (ethanol) without any other additives. The photocatalyst and phthalimide were fruitfully recycled with a simple workup procedure, revealing a high ecoscale value and low environmental factor (E-factor).

Applications of Vanadium, Niobium, and Tantalum Complexes in Organic and Inorganic Synthesis

Organometallic catalysis is a powerful strategy in chemical synthesis, especially with the cheap and low toxic metals based on green chemistry principle. Thus, the selection of the metal is particularly important to plan relevant and applicable processes. The group VB metals have been the subject of exciting and significant advances in both organic and inorganic synthesis. In this Review, we have summarized some reports from recent decades, which are about the development of group VB metals utilized in various types of reactions, such as oxidation, reduction, alkylation, dealkylation, polymerization, aromatization, protein synthesis, and practical water splitting.

Niobium- and zirconium-catalyzed reactions of substituted 2 alkynylamines with Et2Zn

The NbCl5-EtMgBr-catalyzed reaction of N,N-disubstituted 2-alkynylamines with Et2Zn followed by hydrolysis or deuterolysis affords (2Z)-alkenylamines (reduction products of alkyne) in high yields. The reaction of N,N-disubstituted 2-alkynylamines with Et2Zn catalyzed by the Cp2ZrCl2-EtMgBr system occurs as 2-zincoethylzincation, resulting, after deuterolysis or iodinolysis, in the regio- and stereoselective formation of the corresponding dideuterated and diiodinated 2-alkenylamine derivatives with a trisubstituted double bond. This study demonstrates the difference between the catalytic effects of NbCl5 and Cp2ZrCl2 on the pathway of reaction of tertiary 2-alkynylamines with Et2Zn in the presence of catalytic amounts of EtMgBr.

Visible light-mediated cross-coupling of electrophiles: synthesis of α-amino amides from isocyanates and ketimines

Cross-couplings between the electrophilic ketimines and isocyanates are achieved via the visible light-mediated reactivity inversion of the ketimines, affording the desired α-amino amides in high yields, with both metal and metal-free systems.