Lewis Acid‐Catalyzed Sequential Transformations: Straightforward Preparation of Functional Dihydropyridines

Abstract

Lewis acids catalyze the addition of b-enaminoacrylates or b-enaminones to a,b-unsaturated aldehydes leading to substituted dihydropyridines in high yields under mild reaction conditions.

Recent advances in new multicomponent synthesis of structurally diversified 1,4-dihydropyridines

“…Moderate to excellent yields have been obtained by performing the reactions in a stepwise manner (Scheme 3). 11 Later on, the one step, three-component reaction of a 1,3-dicarbonyl compound, primary amine and a,b-unsaturated aldehyde has been realized by Menéndez and coworkers. Their method was established by employing cerium ammonium nitrate (CAN) as a Lewis acid catalyst.…”

Efficient Synthesis of Pyrazoles: Oxidative CC/NN Bond‐Formation Cascade

“…[8] Several studies have shown that enamines bearing a secondary nitrogen atom react with electrophiles preferably at the nucleophilic enamine carbon atom, and that strong electrophiles such as acid chlorides or iso(thio)cyanates are required. [9] Therefore, the reaction with acetonitrile as a rather weak electrophile was unexpected and worth exploration. Moreover, the oxidative formation of NÀN bonds is rare in organic synthesis, often being limited to intramolecular reactions and mostly promoted by strong oxidants like hypervalent iodine(III) reagents.…”

Eco‐Efficient Synthesis of New Pyrido [2, 3‐c] Coumarin Scaffolds Under Sonochemical Method

“…Hantzsch DHP synthesis is one of the most broadly used methods for the preparation of DHPs. In order to improve the efficiency of Hantzsch DHPs synthesis, different catalysts have been explored, and many of them exhibited excellent catalytic activity , such as L‐proline , S‐Valin , Yb(OTf) 3 , molecular I 2 , TBAHS , HOAc , Et 3 N , DBU , Py , ceric ammonium nitrate (CAN) , and so on. These methods, however, suffer from drawbacks such as the use of expensive catalysts, difficulty in availability or preparing the starting materials or catalysts, the environmental pollution caused by utilization of solvents and homogeneous catalysts, low yields, long reaction times, tedious work‐up, waste control, and formation of side products.…”