1,2-Azaborine's Distinct Electronic Structure Unlocks Two New Regioisomeric Building Blocks via Resolution Chemistry

J Am Chem Soc. 2019 Jun 5;141(22):9072-9078. doi: 10.1021/jacs.9b03611. Epub 2019 May 23.

Abstract

Two new 1,2-azaborine building blocks that enable the broad diversification of previously not readily accessible C4 and C5 ring positions of the 1,2-azaborine heterocycle are developed. 1,2-Azaborine's distinct electronic structure allowed the resolution of a mixture of C4- and C5-borylated 1,2-azaborines. The connection between the electronic structure of C4 and C5 positions of 1,2-azaborine and their distinct reactivity patterns is revealed by a combination of reactivity studies and kinetic measurements that are supported by DFT calculations. Specifically, we show that oxidation by N-methylmorpholine N-oxide (NMO) is selective for the C4-borylated 1,2-azaborine, and the Ir-catalyzed deborylation is selective for the C5-borylated 1,2-azaborine via kinetically controlled processes. On the other hand, ligand exchange with diethanolamine takes place selectively with the C4-borylated isomer via a thermodynamically controlled process. These results represent the first examples for chemically distinguishing a mixture of two aryl mono-Bpin-substituted isomers.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Boron Compounds / chemical synthesis
  • Boron Compounds / chemistry*
  • Catalysis
  • Density Functional Theory
  • Heterocyclic Compounds, 1-Ring / chemical synthesis
  • Heterocyclic Compounds, 1-Ring / chemistry*
  • Iridium / chemistry
  • Kinetics
  • Models, Chemical
  • Oxidation-Reduction
  • Thermodynamics

Substances

  • Boron Compounds
  • Heterocyclic Compounds, 1-Ring
  • Iridium