Thiophene-Fused Heteroaromatic Systems Enabled by Internal Oxidant-Induced Cascade Bis-Heteroannulation.

A concise access to thiophene-fused polycyclic π-conjugated systems is described. Methyl aromatic ketoxime acetates, aromatic aldehydes, and elemental sulfur are efficiently assembled in a facile copper-catalytic system through a novel cascade bis-heteroannulation to afford a fused thieno[3,2- d]thiazole motif. The robust nature of this reaction system is reflected by the remarkable simplicity-to-complexity transformation in a one-pot operation, high-yield gram-scale synthesis, and potential applications on the synthesis of high-performance optoelectronic materials.