Mechanochemical Syntheses of N-Containing Heterocycles with TosMIC
A mechanochemical van Leusen pyrrole synthesis with a base leads to 3,4-disubstitued pyrroles in moderate to excellent yields. The developed protocol is compatible with a range of electron-withdrawing groups and can also be applied to the synthesis of oxazoles. Attempts to mechanochemically convert the resulting pyrroles into porphyrins proved to be difficult.
Pyrrolo[1,2-a]quinoxalines from chalcones: An alternate route
The synthesis of 2,4-disubstituted pyrrolo[1,2-a]quinoxalines from chalcones is reported. The key steps used are polyphosphoric acid (PPA) assisted acyl rearrangement of the pyrrole ring and Fe catalyzed reduction-cyclization leading to 2,4-disubstituted
Application of Polyphosphoric Acid-Mediated Acyl Migration for Regiospecific Synthesis of Diverse 2-Acylpyrroles from Chalcones
A metal-free approach for the synthesis of 2-acylpyrroles is reported in this paper. Synthesis of the target molecule started from chalcones and was carried out in two steps. Initial step involved the conversion of chalcones to corresponding 4-substituted-3-acylpyrroles by reaction with TosMIC. In the subsequent step, target molecules were obtained in modest to good yields by polyphosphoric acid-mediated acyl rearrangement of 3-acylpyrroles to their 2-acyl congeners. The crucial final step was amenable to diverse substitutions on pyrrole ring. Preliminary experiment for the determination of mechanism indicated the involvement of acylium ion.
Lithium hydroxide mediated synthesis of 3,4-disubstituted pyrroles
LiOH·H2O in ethanol was found to be an effective reagent for the synthesis of 3,4-disubstituted pyrrole derivatives by the van Leusen method. In situ formation of chalcones from aromatic aldehydes and enolisable ketones, and their subsequent reaction with tosylmethyl isocyanide resulted in the formation and precipitation of pyrrole derivatives from the reaction medium, in good yields. The solvation effect of the polar medium facilitates the reaction. The Royal Society of Chemistry 2013.
Sharma, Ratnesh,Kumar, Kapil,Chouhan, Mangilal,Grover, Vikas,Nair, Vipin A.
p. 14521 - 14527
(2013/09/02)
The pyrrole moiety as a template for COX-1/COX-2 inhibitors
Aroyl- and thiophene-substituted pyrrole derivatives have been synthesized as a new class of COX-1/COX-2 inhibitors. The inhibition of COX-1 was evaluated in a biological system using bovine PMNLs as the enzyme source, whereas LPS-stimulated human monocytes served as the enzyme source for inducible COX-2. The determination of the concentration of arachidonic acid metabolites was performed by HPLC for COX-1 and RIA for COX-2. Variation of the substitution pattern led to a series of active compounds which showed inhibition for COX-1 and COX-2. Structural requirements for the development of COX-1/COX-2 inhibitors are discussed. (C) 2000 Editions scientifiques et medicales Elsevier SAS.