T-shaped molecular building blocks by combined bridgehead and bridge substitution on bicyclo[1.1.1]pentanes.

Derivatives of bicyclo[1.1.1]pentane differentially substituted in bridgehead (1,3) and bridge (2,4) positions have been synthesized. They represent a new T-shaped structural module consisting of a rigid rod with a nearly freely rotating side arm, possibly useful as a molecular building block in syntheses of more complex covalent or supramolecular scaffolds useful in bottom-up construction of molecular level devices or materials. For good chemical connectivity in the axial direction, carboxylates, ethynyls, and acetylsulfanyl groups were installed at the bridgeheads. Quinoxalines were attached in the transverse direction through a highly reactive alpha-diketone system located at the bridges.