Regioselective synthesis of dipyrrolopyrazine (DPP) derivatives via metal free and metal catalyzed amination and investigation of their optical and thermal properties?

RSC Advances Pub Date: 2017-03-24 DOI: 10.1039/C7RA01795B

Abstract

Pyrazine is an important molecular scaffold employed in organic optoelectronic materials. Here we report efficient methods for the synthesis of dipyrrolopyrazine, and pyrrolothieno-pyrazine derivatives that involve regio-selective amination reactions of dihalo-pyrrolopyrazines. The developed protocol readily affords either 2-amino- or 3-amino-pyrrolopyrazines from the corresponding 2-bromo-3-chloro-5H-pyrrolo[2,3-b]pyrazines. When the amination reactions are carried under metal free under microwave irradiation, 3-amino-pyrrolopyrazines are obtained exclusively. In contrast, Buchwald cross coupling of the 2-bromo-3-chloro-5H-pyrrolo[2,3-b]pyrazines affords only 2-amino-pyrrolopyrazine. The pyrrolopyrazine scaffolds were converted to the respective 1,7- and 1,5-dihydrodipyrrolo[2,3-b]pyrazines derivatives using Sonogashira reactions. A comprehensive study of the optical properties, thermal properties, and molecular packing of the synthesized compounds was carried out. The results indicate that the 1,7-derivatives may be promising organic materials for optoelectronic applications.

Graphical abstract: Regioselective synthesis of dipyrrolopyrazine (DPP) derivatives via metal free and metal catalyzed amination and investigation of their optical and thermal properties
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