RESUMEN
The combination of activated carboxylic acids and alcohols/amines to access esters and amides, respectively, is a cornerstone of organic chemistry and has been well developed over the past century. These dehydrations are extensively used in medicinal chemistry and natural product synthesis due to the prevalence of these functional groups in bioactive molecules. Here, we report a divergent process from the expected ester/amide outcomes through a light-induced coupling of activated carboxylic acids and alcohols/amines to efficiently prepare α-hydroxy/amino ketones or ß-ketophosphonates via single-electron chemistry. A phosphorus linchpin strategy allows for the combination of these simple reagents through an intramolecular triplet state radical process, thereby enabling new carbon-carbon bond formation.
RESUMEN
Axially chiral amino acids and its derivatives are vital building blocks of bioactive molecules, artificial peptides, and asymmetric catalysts. Herein, we report an unprecedented carbene-catalyzed atroposelective dynamic kinetic resolution to access axially chiral amino esters via in situ hemiaminals. This protocol features a broad substrate scope and good functional group tolerance and allows the rapid assembly of axially chiral amino esters in good to high yields with high enantioselectivities.
RESUMEN
Although utilization of fluorine compounds has a long history, synthesis of chiral fluorinated amino acid derivatives with structural diversity and high stereoselectivity is still very appealing and challenging. Here, we report a biomimetic study of enantioselective [1,3]-proton shift of ß,ß-difluoro-α-imine amides catalyzed by chiral quinine derivatives. A wide range of corresponding ß,ß-difluoro-α-amino amides were achieved in good yields with high enantioselectivities. The optically pure ß,ß-difluoro-α-amino acid derivatives were further obtained, which have high application values in the synthesis of fluoro peptides, fluoro amino alcohols and other valuable fluorine-containing molecules.
RESUMEN
An unprecedented benzotetramisole (BTM)-catalyzed kinetic resolution for the efficient synthesis of chiral 2H-azirines is described. This protocol provides two chiral isomers in one step with broad scope, good yield and high enantioselectivity. In addition, the optically pure 2H-azirine products have proven to be useful building blocks for further synthetic transformations.
RESUMEN
The unprecedented enantioselective NHC-catalyzed [3 + 3] annulation of α-bromoenals with amidines via a dual C-N bond formation is described. The protocol allows a rapid preparation of 5,6-dihydropyrimidinones in acceptable yields with good enantioselectivities.
RESUMEN
An unprecedented carbene-catalyzed radical trifluoromethylation of olefins with aldehydes in the presence of Togni reagent was developed, thus providing the ß-trifluoromethyl-α-substituted ketones with a broad scope and moderate to high chemical yields. Notably, this process includes a single-electron-transfer process and utilizes the persistent N-heterocyclic-carbene-bound radical as a key intermediate to trigger the cascade radical cross-coupling.
RESUMEN
Higher-order cycloadditions are a powerful strategy for the construction of polycycles in one step. However, an efficient and concise version for the induction of asymmetry is lacking. N-heterocyclic carbenes are widely used organocatalysts for asymmetric synthesis and could be an ideal choice for enantioselective higher-order cycloadditions. Here, we report an enantioselective [10 + 2] annulation between catalytically formed aza-benzofulvene intermediates and trifluoromethyl ketone derivatives. This protocol exhibits a wide scope, high yields, and good ee values, reflecting a robust and efficient higher-order cycloaddition. Density functional theory calculations provide an accurate prediction of the reaction enantioselectivity, and in-depth insight to the origins of stereocontrol.
RESUMEN
A new carbene-catalyzed [4 + 2] annulation of 2 H-azirine-2-carbaldehydes with ketones was developed, thus providing the 2,3-dihydro-6 H-1,3-oxazin-6-one core structures with broad scope and good to excellent yields. Notably, the azolium aza-dienolates generated from the addition of NHCs to 2 H-azirines are first uncovered.
RESUMEN
The unprecedented enantioselective aza-benzoin reaction of aldehydes with 2H-azirines was developed by utilizing a chiral N-heterocyclic carbene as the catalyst. A wide range of corresponding aziridines can be obtained in good yields with high enantioselectivities. The obtained optically active aziridines should be useful in the synthesis of other valuable molecules.
