Organocatalytic domino Knöevenagel–Michael reaction in water for the regioselective synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and pyrido[2,3-d]pyrimidin-2-amines

Abstract

An organocatalyzed aqueous media domino reaction is developed for the regioselective synthesis of benzo[4,5]imidazo[1,2-a]pyrimidines and pyrido[2,3-d]pyrimidin-2-amines.

Pyrimido[1,2-a]benzimidazoles: synthesis and perspective of their pharmacological use

“…A large number of studies [103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118][119][120] devoted to the synthesis of pyrimidobenzimidazoles 157 using MCR of keto esters and their various derivatives 155 as well as malononitrile (156) are presented in general in Scheme 40.…”

“…Keto esters and diketones are important substrates for the construction of the pyrimidobenzimidazole scaffold. [111][112][113][114][115][116][117][118][119][120] In these studies, the present synthetic strategy for the preparation of pyrimidobenzimidazoles corresponds to the approach shown in Scheme 36. The relevance of the research lies in demonstrating the broad capabilities of various catalysts and their systems in MCRs.…”

“…In a number of studies on the preparation of pyrimido-[1,2- a ]benzimidazoles, the catalytic activity of some natural compounds, such as L-proline, 113 thiamine hydrochloride, 114 and citric acid was investigated. 115 Along with all the advantages of organocatalysts, the described procedures are carried out in aqueous media, which expands the field of application of the MCR.…”

Novel magnetic propylsulfonic acid-anchored isocyanurate-based periodic mesoporous organosilica (Iron oxide@PMO-ICS-PrSO3H) as a highly efficient and reusable nanoreactor for the sustainable synthesis of imidazopyrimidine derivatives

“…Because of the importance of imidazopyrimidine scaffold, different homogeneous or heterogeneous acidic catalytic systems have been investigated to promote multicomponent condensation of 2-aminobenzoimidazole, aromatic aldehydes and C-H acids such as dimedone/malononitrile or relevant synthons. Some of the recent examples of reported catalysts are H 6 P 2 W 18 O 62 .18H 2 O 83 , WO 3 -supported sulfonic acid 84 , O-sulfonated poly(vinylpyrrolidonium) hydrogen sulfate 85 , modified ZnO nanoparticles under ball milling conditions 86 , organo-sulfonic acid tags anchored on magnetic titana coated NiFe 2 O 4 nanoparticles 87 , Fe 3 O 4 @GO 88 , magnetic Irish moss 80 , carboxymethyl cellulose 89 , NH 2 SO 3 H 90 , p-toluenesulfonic acid monohydrate 91,92 , Fe 3 O 4 @clay 93 , L-proline 94 , molecular iodine 95 , polyethylene glycol methacrylate-grafted dicationic imidazolium-based ionic liquid 96 and NaHSO 4 modified phenylene bridged periodic mesoporous organosilica magnetic nanoparticles 55 . In spite of their merits, the existing methodologies have drawbacks such as low to moderate yields, difficulties in the catalyst recovery and product isolation, toxic or expensive catalysts, lengthy reaction times, the use of volatile organic solvents or significant amounts of waste materials production 97 .…”

Preparation and characterization of copper/polysulfonamide complex immobilized on geraphene oxide as a novel catalyst for the synthesis of pyrimido[1,2‐a]benzimidazoles

“…[ 7 ] The one‐pot three‐component condensation reaction between β‐dicarbonyl compounds, aldehydes, and 2‐amino‐1 H ‐benzimidazole is a well‐known technique for the preparation of pyrimido[1,2‐a]benzimidazoles. These methods employed diverse catalysts such as silica‐supported sulfuric acid, [ 8 ] poly(vinylpyrrolidonium)perchlorate, [ 9 ] l ‐proline, [ 10 ] magnesium oxide, [ 11 ] and N , N , N ′, N ′‐tetrabromobenzene‐1,3‐disulfonamide (TBBDA). [ 12 ] Many of the recent reported protocols have interesting merits, but some suffer from one or more disadvantages such as harsh reaction conditions, tedious workup procedures, long reaction times, and emission of hazardous materials into environment.…”