Stereomutation of Substituted Bullvalenes

The
stereomutation of substituted bullvalenes is an inevitable
consequence of the valence isomerism that automerizes this unique
fluxional hydrocarbon. The introduction of external stereogenicity
in the substituents expands the reaction graphs and leads to a wealth
of complex diastereochemical relationships. In this communication,
we explore these possibilities and prepare a range of stereochemically
rich substituted bullvalenes. This includes a series of disubstituted
bullvalenes with two external stereocenters as a platform for fluxional,
shape-diverse compound libraries. We also prepare a tethered bisbullvalene
with central stereogenicity in the tether as an ensemble of 900 unique
isomers that are completely stereomutable.