Stereoselective Iterative Convergent Synthesis of <i>Z</i>‑Oligodiacetylenes from Propargylic Dithioacetals

A series of ^<i>t</i>Bu-substituted <i>Z</i>-oligodiacetylenes (<i>Z</i>-ODAs) are synthesized from the reactions of allenyl/propargylic zinc reagents, obtained from the corresponding propargylic dithiolanes and BuLi, with dithiolane-substituted propargylic aldehydes followed by stereospecific elimination of β-thioalkoxy alcohols under Mitsunobu conditions. The stereochemical assignments are based on NOE experiments. The X-ray structure of the hexamer further supports the <i>Z</i> configuration for each of the double bonds in these ODAs. The photophysical properties of these <i>Z</i>-ODAs have been examined and are compared with known related <i>E</i>- and <i>Z</i>-ODAs with different substituents