Nitrothiophenes as electrophiles in polar Diels-Alder reactions. Solvent effect and microwave irradiation

Pedro Mancini,Claudia D Della Rosa

doi:10.3390/ecsoc-17-c004

Abstract

In this work the electrophilic behaviour of nitrothiophenes in polar Diels-Alder toward dienes of different nucleophilicity is studied. In thermal conditions the reactions were development in molecular solvents and in protic ionic liquids trying to compare the solvent effects on this class of reactions. In the presence of these solvents the reaction system was exposed to microwave irradiation as a complement of reaction conditions.

Highlights

The Diels–Alder (DA) reaction is one of the most useful processes in preparative organic chemistry
We report our findings electrophilic behaviour of nitrothiophenes when they were exposed to different dienes strongly, moderately and poorly activated, under thermal conditions, using molecular solvents and ionic liquids and in some experiences combining it with microwave irradiation
We started the study employing the 2-nitrothiophene 1 with 2 in a sealed ampoule (150 oC, 72 h) using benzene as solvent. In this reaction it was observed pyrrolyl-thiophene 5 as the principal product formed by an assumed hetero cycloaddition.9(Scheme 2, Table 1, entry 1)

Summary

Introduction

The Diels–Alder (DA) reaction is one of the most useful processes in preparative organic chemistry. Its potential in heterocyclic chemistry and natural products synthesis is very well known. It provides the chemist with one of his best tools for the preparation of cyclic compounds having a six-membered ring. The process is in one step inter or intramolecular from a diene and a dienophile bearing an almost unlimited number of variants. It is worth noting that these variants exist in the substitution of the reaction component and in the electronic nature of these dienes and dienophiles. In the 1980s, studies of aromatic heterocycles such as indoles, benzofurans, pyrroles, furans, and thiophenes part of DA reactions demonstrate the viability of these systems as dienophiles.[4]. We report our findings electrophilic behaviour of nitrothiophenes when they were exposed to different dienes strongly, moderately and poorly activated, under thermal conditions, using molecular solvents and ionic liquids and in some experiences combining it with microwave irradiation

Results and discussion

Scheme 2

Conclusion