Fourfold Diels–Alder Reaction of Tetraethynylsilane

Abstract

A series of ethynylated silanes, including tetraethynylsilane, was treated with tetraphenylcyclopentadienone at 300 °C under microwave irradiation to give the aromatized Diels-Alder adducts as sterically encumbered mini-dendrimers with up to 20 benzene rings. The sterically most congested adducts display red-shifted emission through intramolecular π-π interactions in the excited state.

Recent Advances in Click Chemistry Applied to Dendrimer Synthesis

“…During this specific case, a carbon monoxide molecule is lost, preventing any retro Diels-Alder (rDA). According to our survey, the conditions to carry out this reaction have not evolved noticeably within the last five years, except for the use of microwave irradiation to reach 300 °C [111]. With this optimization, Bunz et al ., were able to reach new levels of steric hindrance in a dendrimer.…”

“…Fessner et al ., screened several activated alkyne for CuAAC in their 2010 article and they managed to functionalize a POSS core with adamantane units [85]. The article of Bunz discussed above can also be seen as a type of difficult decoration that was enabled by click chemistry [111]. In a publication by the Tang group, propiolic acid was used with a source of copper to activate the reaction both through the catalytic and the EWG strategies at the same time to add a bulky decoration on a congested G4 dendrimer [150].…”