Cooperative and Enantioselective NbCl₅/Primary Amine Catalyzed Biginelli Reaction

Abstract

A series of chiral organocatalysts and Lewis acids have been evaluated in the Lewis acid/organocatalysts‐based cooperative catalytic Biginelli reaction, which resulted in the determination of a novel cooperative Lewis acid/primary amine catalyst system, NbCl5/QN‐NH2. The synergistic effect of NbCl5 and the quinine‐derived primary amine is pronounced and gave dihydropyrimidiones (DHPMs) in moderate to good enantioselectivities (up to 84 % ee) and good to excellent yields (up to 99 % yield) under mild conditions.

Cu(II) immobilized on mesoporous organosilica as an efficient and reusable nanocatalyst for one‐pot Biginelli reaction under solvent‐free conditions

“…This method is based on one‐pot condensation of an aldehyde, urea, and a β ‐ketoester that proceeds under strongly acidic conditions . Due to the importance of the Biginelli reaction products (DHPMs), numerous improvements have been developed with different types of catalysts such as ionic liquids or supported ionic liquids, dodecyl sulfonic acid (DSA), NbCl 5 , Gly(NO 3 ), Cu(NO 3 ) 2 ·3H 2 O, mesoporous SiO 2 ‐H 2 PO 3 , Fe 3 O 4 @Nb 2 O 5 , β ‐Cyclodextrin‐propyl sulfonic acid, Lanthanide Triflate, hydrotalcite, ZrO 2 –Al 2 O 3 –Fe 3 O 4 , ErCl 3 , nano‐γ‐Fe 2 O 3 ‐SO 3 H, Fe 3 O 4 @mesoporous SBA‐15, and various conditions such as solvent‐free, ultrasound, microwave synthesis, and the grindstone technique . However, there is scope for further improvement toward milder reaction conditions, and better yields.…”

Development and efficient 1-glycyl-3-methyl imidazolium chloride–copper(II) complex catalyzed highly enantioselective synthesis of 3, 4-dihydropyrimidin-2(1H)-ones

“…The catalytic reaction which can be carried out with a small amount of expensive complexes is the most useful feature of synthetic reaction involving copper complex. According to literature, Li-Wen Xu [29] and co-workers obtained good yield in the asymmetric Biginelli reaction using 10 mol% of air and water stable Cu(OTf) 2 in the presence of 1,4-dioxane. Among the previous report, increasing the quantity of the catalyst can improve the reaction yield and shorten reaction time (Table 4).…”

“…Zhiwei Miao [27] and Shi-Wei Luo et al [28], organocatalyst modified by 3,3 0 -disubstituents of phosphoric acids or chiral bifunctional primary amineethiourea catalysts: for enantioselective Biginelli reaction in the presence of organic co-solvent. Furthermore; Li-Wen Xu et al, was achieved the high enantioselective in presence of NbCl 5 /primary amine [29].…”

Title Pages

“…54 Chiral 2-tert-aminoureas, however, are catalysts of choice for asymmetric iodolactonization 55 , and multifunctional Cinchona-based 2,2′-diaminothioureas for asymmetric phospha-Michael addition 56 , while 'plainand-simple' S-tritylcysteine is seemingly ideal for asymmetric thia-Michael addition 57 . Cooperative asymmetric organocatalysis has also evolved, as manifested in a recent asymmetric epoxidation of α-branched enals in the presence of a quinine-based primary amine and a chiral Brønsted acid 58 ; by the same token, an asymmetric Biginelli synthesis benefits from the cooperation of the same aminocatalyst and NbCl 5 as Lewis acid 59 . More remarkable, perhaps, is the parallel kinetic resolution of alcohols in one pot with a combination of a chiral amine and phosphine, wherein two different anhydrides react preferentially and simultaneously with one or other of the substrate enantiomers 60 .…”