Molecular Rods Based on Oligo-spiro-thioketals

We report on an extension of the
previously established concept
of oligospiroketal (OSK) rods by replacing a part or all ketal moieties
by thioketals leading to oligospirothioketal (OSTK) rods. In this
way, some crucial problems arising from the reversible formation of
ketals are circumvented. Furthermore, the stability of the rods toward
hydrolysis is considerably improved. To successfully implement this
concept, we first developed a number of new oligothiol building blocks
and improved the synthetic accessibility of known oligothiols, respectively.
Another advantage of thioacetals is that terephthalaldehyde (TAA)
sleeves, which are too flexible in the case of acetals can be used
in OSTK rods. The viability of the OSTK approach was demonstrated
by the successful preparation of some OSTK rods with a length of some
nanometers.