A Pummerer Reaction-Enabled Modular Synthesis of Alkyl Quinoline-3-carboxylates and 3-Arylquinolines from Amino Acids

Concise synthesis of functionalized quinolines has received continuous research attention owing to the biological importance and synthetic potential of bicyclic N-heterocycles. However, synthetic routes to the 2,4-unsubstituted alkyl quinoline-3-carboxylate scaffold, which is an important motif in drug design, remain surprisingly limited, with modular protocols that proceed from readily available materials being even more so. We herein report an acidic I₂-DMSO system that converts readily available aspartates and anilines into alkyl quinoline-3-carboxylate. This method can be extended to a straightforward synthesis of 3-arylquinolines by simply replacing the aspartates with phenylalanines. Mechanistic studies revealed that DMSO was activated by HI via a Pummerer reaction to provide the C1 synthon, while the amino acid catabolized to the C2 synthon through I₂-mediated Strecker degradation. A formal [3 + 2 + 1] annulation of these two concurrently generated synthons with aniline was responsible for the selective formation of the quinoline core. The synthetic utility of this protocol was illustrated by the efficient synthesis of human 5-HT4 receptor ligand. Moreover, an unprecedented chemoselective synthesis of 2-deuterated, 3-substituted quinoline, featuring this reaction, has been established.

Efficient synthesis of (E)-2-nitromethylcinnamatesviaphosphine-catalyzed tandem α-addition and 1,3-rearrangement

An efficient synthetic approach for accessing (E)-2-nitromethylcinnamatesviaa phosphine-promoted tandem reaction between substituted nitromethanes and alkynes has been developed.

Synthetic Approach to the Preparation of (2-Acetoxy)allyl Nitro Compounds

A synthetic approach to a new class of allyl nitro derivatives is reported. (2-Acetoxy)allyl nitro compounds have been prepared for the first time in a four-step procedure by a preliminary reaction of nitroalkanes with 2-(phenylselenyl)acetaldehyde. After the acetylation of the obtained nitro alcohols, the unsaturation is installed by an oxidation reaction involving the phenylselenyl group followed by a thermal elimination. The oxidation process is accomplished under flow conditions ensuring a notable lowering of overoxidation by products observed in batch.

Rhodium-catalyzed ortho C–H bond activation of arylamines for the synthesis of quinoline carboxylates

A diverse catalytic approach for the synthesis of quinoline derivatives via Rh catalyzed ortho C–H activation of aryl amines with alkynic esters is described.