Synthesis and chiroptical properties of optically active, regioregular oligothiophenes.

[reaction: see text] A series of regioregular oligothiophenes bearing chiral oxazoline residues have been synthesized in high yields by a stepwise synthesis using the Stille cross-coupling reaction. The chiroptical properties of the oligothiophenes up to the octamer were investigated with UV-visible and CD spectroscopies. The octamer showed split-type Cotton effects in chloroform as a good solvent in the presence of a poor solvent such as acetonitrile, while the lower molecular weight oligomers exhibited almost no induced CD.