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Synthesis of Benzo‐ and Naphthoquinonyl Boronic Acids: Exploring the Diels–Alder Reactivity
Author(s) -
Veguillas Marcos,
Redondo Maria C.,
García Isabel,
Ribagorda María,
Carmen Carreño M.
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902796
Subject(s) - chemistry , boronic acid , substituent , reactivity (psychology) , regioselectivity , organic chemistry , diene , yield (engineering) , catalysis , medicine , natural rubber , alternative medicine , materials science , pathology , metallurgy
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.