A novel "double-coupling" strategy for iterative oligothiophene synthesis using orthogonal Si/Ge protection.

[reaction: see text] A new iterative synthesis of regioregular oligothiophenes has been developed in which "double-coupling" after each iteration minimizes deletion sequences. The method exploits the susceptibility of alpha-silyl- but not alpha-germyl-substituted thiophene derivatives toward nucleophilic ipso-protodemetalation and features an unusual "base-free" Suzuki-type cross-coupling protocol. The strategy has been designed for the solid-phase synthesis of high purity oligothiophenes using a germanium-based linker.