Harnessing the ambiphilicity of silyl nitronates in a catalytic asymmetric approach to aliphatic β3-amino acids

Nitronate anions, formally generated by α-deprotonating the corresponding nitroalkanes, are highly nucleophilic and versatile intermediates in many carbon–carbon bond-forming reactions. In contrast, the corresponding silyl nitronates are ambiphilic and react, at the same carbon atom, with both electrophiles and nucleophiles. However, while their nucleophilicity has been well exploited in catalytic enantioselective reactions with imines and aldehydes, utilizing the electrophilicity of silyl nitronates in asymmetric synthesis has remained elusive. Here we report the facile, efficient and general reactivity of readily available silyl nitronates with silyl ketene acetals, catalysed by highly Lewis-acidic and confined silylium imidodiphosphorimidate catalysts. The products of this reaction, so-called nitroso acetals, are obtained in excellent enantioselectivity and can be easily converted into N-Boc-β3-amino acid esters in a single step.

Synthesis of Derivatives of closo-Dodecaborate Anion Based on Amino Acid Esters

This work proposes a new method for the synthesis of N-borylated amino acids based on nucleophilic substitution reactions in the [B12H11IPh]– anion. Esters of glycine and L-phenylalanine were used as nucleophiles. The structure of the products has been determined by multinuclear NMR spectroscopy, IR spectroscopy, and ESI mass spectrometry.

Bismuth vanadate: A versatile heterogeneous catalyst for photocatalytic functionalization of C(sp2)–H bonds

Bismuth vanadate (BiVO4) could be prepared by the hydrothermal kettle method. Herein, the synthesized BiVO4-180 is demonstrated to be a versatile and stable heterogeneous photocatalyst for a series of C(sp2)–H functionalization reactions under visible light irradiation at ambient conditions. A series of functionalized compounds such as tetrahydroquinolines, 3-arylmethyl indoles, α-aryl α-amino acid esters, and sulfurized/selenized/thiocyanated heterocycles were successfully synthesized in good yields (>70 examples, including modification of drugs and peptides). The BiVO4 photocatalyst has the advantages of being recyclable, low-cost, air-tolerant, and high efficiency, which is the typical characteristic of overcoming the shortcomings of homogeneous catalysts.

Group-Assisted-Purification Chemistry Strategy for the Efficient Assembly of Cyclic Fused Pyridinones

A group-assisted-purification (GAP) chemistry strategy based Ugi four-center three-component reaction (Ugi-4C-3CR) was explored. The reaction proceeded well to deliver the cyclic fused pyridinones selectively. Moreover, the reaction condition was mild and avoided additional chromatography or recrystallization work-up. Also, wide variations in substrates, such as anilines and aliphatic amines as well as amino alcohols and amino acid esters were all tolerated and achieved in good to excellent yields. Importantly, ladder-type cyclic fused pyridinones can be further constructed with excellent yield of 91%.