Synthesis of dithieno[2,3-b:3′,2′-d]thiophenes-building blocks for cross-conjugated β-oligothiophenes

Syntheses of annelated and functionalized ss-trithiophenes (dithieno[2,3-b:3 ',2 '-d]thiophenes), building blocks for the helically annelated, cross-conjugated ss-oligothiophenes, are reported. UV-vis spectra reveal that the effect of octyl substituents on the onset of electronic absorption in annelated ss-trithiophenes is negligible compared to the effect of helical distortion in the higher ss-oligothiophenes.