Modular synthetic strategies for dipyrrolopyrazines

Herein we describe the synthesis of dipyrrolopyrazines via a tandem-Sonogashira coupling with subsequent direct cyclisation of the resulting bisalkynes. The key precursor, di-tert-butyl (3,6-dichloropyrazine-2,5-diyl)dicarbamate, can be easily obtained on a large scale. Bidirectional cross-couplings yield either the diyne or dipyrrolopyrazine scaffolds selectively. When the intermediate bisalkynes are cyclised with IPrAuNTf2, an in situ deprotection of the Boc-group is observed, giving access to the N-unsubstituted dipyrrolopyrazines. Functionalisation of the pyrrolo-CH or NH-moiety allows further adjustment of solubility, processability and optoelectronic properties. Photophysical studies demonstrate remarkable stability and high quantum yields. Our work presents novel synthetic approaches for dipyrrolopyrazines. Modifying pyrrole and NH-moieties enhances versatility, facilitating their utilisation in materials science applications.