A Metal-Free Cyclobutadiene Reagent for Intermolecular [4 + 2] Cycloadditions
Benjamin R. Boswell, Carl M. F. Mansson, Gabrielle E. Cabrera, Calvin Hansen, Allen G. Oliver, Noah Z. Burns
Abstract
Cyclobutadiene is a highly reactive antiaromatic hydrocarbon that has fascinated chemists for over 60 years. However, its preparation and uses in chemical synthesis are sparing, in part due to its lengthy synthesis that generates hazardous byproducts including excess heavy metals. Herein, we report a scalable, metal-free cyclobutadiene reagent, diethyldiazabicyclohexene dicarboxylate, and explore its intermolecular [4 + 2] cycloaddition with various electron-deficient alkenes. We also demonstrate its utility in a three-step synthesis of dipiperamide G and a diverse array of product derivatizations including bromocyclobutadiene.
Topics & Concepts
CyclobutadieneChemistryAntiaromaticityReagentIntermolecular forceCycloadditionComputational chemistryCombinatorial chemistryOrganic chemistryMoleculeCatalysisAromaticityAsymmetric Synthesis and CatalysisCyclopropane Reaction MechanismsChemical Reactions and Mechanisms