Network Analysis of Substituted Bullvalenes

Abstract

Substituted bullvalenes are dynamic shape-shifting molecules that exist within complex reaction networks. Herein, we report the synthesis of di-and trisubstituted bullvalenes and investigate their dynamic properties. Trisubstituted bullvalenes share a common major isomer which shows kinetic metastability. A survey of the thermodynamic and kinetic landscapes through computational analysis together with kinetic simulation provides a map of the internal dynamics of these systems.

Shapeshifting molecules: the story so far and the shape of things to come

“…While this article was under review, Fallon reported the successful application of this protocol to prepare trisubstituted BV derivatives. 20 Trisubstituted analogues of 1 are prepared in overall yields of 24-50% using trimethylsilylcyclooctatetraene in place of cyclooctatetraene.…”

“…Fallon et al built upon this isomer coding system for the network analysis of BV derivatives by developing an algorithm that integrates it with quantum-chemical energy calculations. 9,20 The algorithm generates all the possible BV structures in the dynamic network, identifying enantiomeric pairs and interconnections (i.e., transition states 11 ) between isomers. The geometry of each isomer is then optimised and their single-point energies are calculated through the ORCA 4.0 programme package, 21 forecasting the equilibrium distribution of isomers.…”

“…Care will need to be taken when designing systems to minimise the inherent Gibbs free energy differences between isomers. The introduction of substituents to the BV core has been found 7f, 9,20 to favour a small number of isomers by energy differences on the order of >40 kJ mol À1 , which would likely limit the sensitivity of the system to small changes in noncovalent bonding interactions. There is also considerable scope to investigate the use of alternative end groups, diverging from the boronic acid and porphyrin chemistry employed to date.…”

Boronate Ester Bullvalenes

“…22 The origin of this kinetic feature was explored in a recent study by our laboratory and traced to high barriers in the first and second generation isomerisation from isomer A. 23 DFT analysis and kinetic modelling of triphenylbullvalene predict an isomer A half-life of 4.5 min (see SI for full details).…”

Construction of vicinal 4°/3°-carbonsviareductive Cope rearrangement

“…Thus, the reaction appears to be uxional/shape-shiing at room temperature. [36][37][38][39][40] For this substrate, we also modelled the dissociative pathway (Scheme 2D). It was found that bond breakage to two allylic radical intermediates is a higher energy process than the concerted transition state (Scheme 2C vs. Scheme 2D).…”