Synthesis of Monodisperse Oligo(para-phenyleneethynylene)s Using Orthogonal Protecting Groups with Different Polarity for Terminal Acetylene Units

Abstract

Monodisperse oligo(para-phenyleneethynylene)s (oligoPPEs) were synthesized by a divergent-convergent synthesis starting from 1,4-dihexyl-2-(3-hydroxyprop-1-ynyl)-5-[2-(triisopropylsilyl)ethynyl]benzene and using the Pd/Cu-catalyzed alkyne-aryl coupling. The groups hydroxymethyl (HOM) and triisopropylsilyl (TIPS) function as orthogonal protective groups for the acetylene moieties. The polar HOM group shows a strong impact on the chromatographic behaviour of the products and makes the isolation of pure compounds very easy. The synthesis was pursued up to the nonamer. The oligoPPEs were fully characterised, including absorption and emission spectral data.