Can electrostatic catalysis of Diels-Alder reactions be harnessed with pH-switchable charged functional groups?

Heather M. Aitken, Michelle L. Coote

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)

Abstract

Quantum-chemical calculations at the M06-2X/6-31+G(d,p) and G3(MP2)CC levels of theory are used to assess the feasibility of harnessing charged functional groups to electrostatically catalyse Diels-Alder reactions and alter their regio selectivity. For the reaction of the polar diene 2-pyrone with substituted cyclopentene, pH switches of nearly 60 kJ mol-1 are observed in the gas-phase. To switch regioselectivity however it is necessary to toggle between negatively and positively charged functional groups. With the 6-membered cyclohexene derivatives, similar pH-switches are observed but this time an opportunity to pH-switch diastereomeric selectivity is also observed due to the asymmetry of the transition state. When 2-pyrone was replaced with a non-polar diene, cyclopentadiene, pH switches were understandably smaller but still substantial (ca. 15 kJ mol-1). Likewise pH switches are attenuated by solvent but remain substantial (ca. 30 kJ mol-1) in toluene and synthetically useful (ca. 15 kJ mol-1) even in moderately low polar solvents such as dichloromethane.

Original languageEnglish
Pages (from-to)10671-10676
Number of pages6
JournalPhysical Chemistry Chemical Physics
Volume20
Issue number16
DOIs
Publication statusPublished - 28 Apr 2018
Externally publishedYes

Keywords

  • Electrostatics
  • Diels–Alder reactions
  • Solvents

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