Stereomutation of Substituted Bullvalenes

Abstract

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.

Guest‐Dependent Isomer Convergence of a Permanently Fluxional Coordination Cage

“…However, all experimental evidence indicates isomer B as the predominant ligand isomer within the cage. This isomer is axially chiral, and its Plus/Minus ( P/M ) descriptors are defined by considering an axis that runs from the centre point of the cyclopropane through the apical bridgehead (or apex) of bullvalene [5d] . Within the cage, isomer B also possesses a vertical directionality relative to an arbitrary top‐view of the cage, which we define as the up/down tilt of the apex.…”

The Journey to Fluorescent Bullvalenes: Pitfalls and Prospects

“…This route starts with a Co‐catalyzed [6+2] cycloaddition [5] of cyclooctatetraene ( 1 ) with acetylene derivatives, followed by a photo‐induced di‐π‐methane rearrangement of the resulting intermediate bicyclo[4.2.2]deca‐2,4,7,9‐tetraene derivatives ( 2 b , BDT) to eventually yield the bullvalenes in moderate to high yields (Scheme 1). [6] With this synthetic route, a large series of compounds has been synthesized and investigated, for example, with respect to their interconverting networks, their supramolecular association with cyclodextrins, metal ions, bacteria, and proteins [6–14] …”

Ambimodal Pericyclic Rearrangements of Dialkenyl-Bullvalenes Give Tetrahydro-1,8-ethenoheptalenes

“…However, this fascinating topic was largely abandoned for decades until a recent revival with major contributions from Bode, Echavarren, and our own laboratory . Recently, we reported the synthesis of a set of boronate ester functionalized bullvalenes, opening up unparalleled access to substituted derivatives …”

“…Geometry optimizations were calculated using the B3LYP functional, employing Grimme’s empirical D3BJ dispersion correction together with the Def2-SVP basis set. , Single-point energy calculations were done using the same functional and the Def2-TZVPPD , basis set. All calculations were performed using the ORCA 4.2.1 program package. , This procedure has performed well in our previous studies with bullvalene population distributions. , …”