Use of a 9,10-Dihydrofulvalene Pincer Cycloadduct as a Cornerstone for Molecular Architecture

Abstract

Dimethyl-3,3a,3b,4,6a,7a-hexahydro-3,4,7-metheno-7H-cyclopenta[a]pentalene-7,8-dicarboxylate (3, a 9,10-dihydrofulvalene pincer cycloadduct) was found to be a versatile building block for the synthesis of polynorbornyl scaffolds containing various end functionalities such as porphyrins, pyrimidine, and the phenanthroline ligand in the free and complexed forms. The block is stable under various cycloaddition reaction conditions and has high p-bond reactivity. Molecular modelling using a semi-empirical based method (AM1) shows that incorporation of this diene block into polynorbornyl systems has an important influence on their overall architecture. In particular, incorporation of the block results in a straightening of the curvature normally observed in polynorbornyl molecules to form almost ideally linear polycyclic rigid spacers.