Oxidative Aromatization of Pyrazolines

Title:Oxidative Aromatization of Pyrazolines

Volume: 14 Issue: 5

Author(s): Izamara Casadia, Danilo Yano de Albuquerque, Adriana do Carmo Capiotto, Claudio Martin Pereira de Pereira and Lucas Pizzuti*

Affiliation:

• Faculty of Exact Sciences and Technology, Federal University of Grande Dourados, ZC: 79825-070, Dourados-MS,Brazil

Keywords: Dehydrogenation, dehydrogenative aromatization, 4, 5-dihydro-1H-pyrazoles, oxidative aromatization, pyrazoles, pyrazolines.

Abstract: Background: Pyrazole derivatives have remained a much studied class of heterocyclic compounds with application in several scientific areas such as agrochemicals, pharmaceuticals and building blocks for more elaborated structures. The cyclocondensation of enones with hydrazine derivatives is one of the most valuable ways of synthesizing pyrazole derivatives. This method produces a racemic mixture of 4,5-dihydro- 1H-pyrazoles also known as pyrazolines which can be converted into aromatic pyrazoles by oxidative aromatization.

Objective: The aim of this review article is to cover the state of the art oxidative aromatization of pyrazolines to pyrazoles.

Method: It was performed a comprehensive compilation from the literature concerning the reported methods for oxidative aromatization of pyrazolines from the last thirty years. The review of each method was presented along with a critical point of view.

Results: Several oxidant systems were applied for converting pyrazolines into pyrazoles. Most of the reviewed protocols proved to be efficient for oxidize 1,3,5-trisubstituted pyrazolines when the group attached to the N1 was H, methyl and (substituted)-phenyl. On the other hand few methods were found to dehydrogenate pyrazolines containing other than the above groups on N1 such as (thio)carbamoyl and amidinyl.

Conclusion: Conversion of pyrazolines into aromatic pyrazoles by oxidative aromatization attracted attention in the last decades. A range of reagents has been reported for this purpose, but there is still the need for developing general methods that fill the requirements of green chemistry and that are applicable for more elaborated substrates.

Cite this article as:

Casadia Izamara, de Albuquerque Yano Danilo, Carmo Capiotto do Adriana, Pereira de Pereira Martin Claudio and Pizzuti Lucas*, Oxidative Aromatization of Pyrazolines, Current Organic Synthesis 2017; 14 (5) . https://dx.doi.org/10.2174/1570179414666161230151123

DOI https://dx.doi.org/10.2174/1570179414666161230151123	Print ISSN 1570-1794
Publisher Name Bentham Science Publisher	Online ISSN 1875-6271