One or more nitrogen‐containing molecules constitute an important class of heterocyclic compounds in organic synthesis, due to their reactivity and their presence in many molecules of natural, human or plant origin. These nitrogenous heterocycles play an essential role in various scientific domains, whether they are chemical, biological or pharmacological. N‐heterocycles are the privileged source of many research topics developed by several groups of researchers. Thus, different methods have been developed to access these heterocyclic compounds with nitrogenous rings, such as triazolopyrimidines. In this review, a bibliographic study summarizing the pharmacological importance of the triazolo[1,5‐a]pyrimidine ring, the different synthesis routes of these derivatives as well as their reactivity was reported.
The 2-(alkylcarbonyl)benzoic acids obtained by esterification of phthalic anhydride are converted into azide derivatives: alkyl 2-[(azidocarbonyl)amino]benzoates and to ureas: dialkyl 2,2′-[carbonylbis(azanediyl)]dibenzoates. These transformations were carried out using classical Curtius rearrangement conditions in the presence of diphenylphosphoryl azide (DPPA) in a basic medium, followed by hydrolysis. Subsequently, a final condensation reaction of these urea derivatives enabled us to obtain, for the first time, the new alkyl derivatives, alkyl 2-[2,4-dioxo-1,2-dihydroquinazolin-3(4H)-yl]benzoates. All the new compounds obtained in satisfactory yields were characterized by 1H and 13C NMR, and by X-ray crystallographic analysis.
Background:
In this current work, a new synthesis strategy was developed to obtain 1,3,4-trisubstituted pyrazoles derivatives.
Methods:
A series of 1,3,4-trisubstituted pyrazoles have been prepared via 1,3-dipolar cycloaddition reaction of 3-phenylsydnones with a variety of alkenes derivatives, symmetric and non-symmetric alkynes derivatives, N-phenyl-maleimide, N-benzyl-maleimides and maleic anhydride under conventional manner.
Results:
Moreover, in this work it has been demonstrated that the 4-bromopyrazole intermediates can be further functionalized by a combination of Suzuki-Miyaura cross coupling reactions with aryl-boronic acids and N-arylation reactions of anilines.
Conclusion:
In summary, we have developed a new method to obtain 1,3,4 triarylated pyrazoles through 3-phenylsydnone 1,3-dipolar cycloadditions. By comparing the different reactions, it is apparent that high temperatures and xylene as solvent are key to achieve pyrazoles derivatives and the best yields were observed for symmetric and non-symmetric alkynes as dipolarophiles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.