Alkynylated Diazadioxaacenes: Syntheses and Properties

We
report the successful synthesis of a series of ethynylated dioxa­diazaacenes
and investigate their properties. We developed a modular Cu-based
catalytic procedure to build up [1,4]­dioxino­[2,3-b]­pyrazine motifs starting from only a few building blocks. TIPS-acetylene-substituted
benzene-1,2-diol and naphthalene-2,3-diol were reacted with 2,3-dichloropyrazine,
2,3-dichloroquinoxaline, and 2,3-dichlorobenzoquinoxaline to give
a set of six novel and well-soluble dioxadiazaacenes. Different reaction
conditions for the coupling were tested. Copper catalysis is most
effective and gave the best yield of dioxadiazaacenes. The resulting
azaoxaacenes were characterized in terms of optical and electronic
properties and crystal packing.