2,3-Dichloroquinoxaline as a versatile building block for heteroaromatic nucleophilic substitution: A review of the last decade

Abstract

Nucleophilic aromatic substitution (SNAr) is a class of reaction that has become very important over time. This type of transformation usually proceeds without the use of metal catalysts, making it very important for pharmaceutical and industrial purposes. Nevertheless, in order to obtain the desired substituted product, activated substrates are required to allow SNAr reactions under mild conditions. In this context, quinoxaline derivatives are one class of N-heteroarenes that has attracted great attention from the scientific community because of the large variety of applications for their derivatives in many fields, such as biological and technological areas. There are several reported methods for the synthesis of quinoxaline derivatives. Nonetheless, reactions of 2,3-dichloroquinoxaline (DCQX) with nucleophilic species has become a viable alternative because of the possibility to form new carbon-heteroatom bonds (e.g. CO, CN, and CS) directly at C2 and/or C3 positions of the quinoxaline moiety. This current review brings an overview of the last decade on the remarkable versatility of DCQX as a substrate for SNAr reactions. Herein, we show several examples in which DCQX reacts with N-, O-, S-, P- and C-nucleophiles, including controlled processes for the selective formation of mono- and disubstituted substrates. Almost all polyfunctionalized quinoxalines synthesized using this approach have shown applications in different areas such as in biological and technological fields. Keywords: 2,3-Dichloroquinoxaline, Building block, Heteroaromatic nucelophilic substitution, Organic synthesis