Synthesis of benzo- and naphthoquinonyl boronic acids: exploring the Diels-Alder reactivity

Chemistry. 2010 Mar 22;16(12):3707-19. doi: 10.1002/chem.200902796.

Abstract

Substituted 2-quinonyl boronic acids have been synthesised from 1,4-dimethoxy aromatic derivatives in two steps: regiocontrolled boronation and oxidative demethylation. The study of their dienophilic behaviour evidenced that the boron substituent significantly increases the reactivity and triggers an efficient domino process in which the Diels-Alder reaction was followed by a protodeboronation or dehydroboronation, depending on the substitution on both the quinone and diene partners. The boronic acid acts as a temporary controller, opening a direct access to trans-fused meta-regiosomeric adducts when 3-methyl-substituted 2-quinonyl boronic acids react with dienes with a substituent at C-1. A particularly valuable synthetic result was obtained in the reaction between 3,6-dimethyl-2-quinonyl boronic acid and piperylene under an oxygen atmosphere; trans-fused 8a-hydroxy-2,4a,8-trimethyl tetrahydronaphthoquinone was formed directly, in excellent yield and in a highly diastereoselective manner.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzoquinones / chemistry*
  • Boronic Acids / chemistry*
  • Crystallography, X-Ray
  • Hydrogen Bonding
  • Molecular Conformation
  • Oxidation-Reduction
  • Stereoisomerism

Substances

  • Benzoquinones
  • Boronic Acids
  • quinone