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The photoenol tautomer of 5-methyl-1, 4-naphthoquinone

✍ Scribed by Erika Rommel; Jakob Wirz

Publisher
John Wiley and Sons
Year
1977
Tongue
German
Weight
326 KB
Volume
60
Category
Article
ISSN
0018-019X

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✦ Synopsis

Abstract

Irradiation of pale yellow 5‐methyl‐1, 4‐naphthoquinone (1, Scheme 1) yields the blue photoenol 4‐hydroxy‐5‐methylidene‐1(5__H__)‐naphthalenone (2) which is stable at 77 K. At room temperature the enol retautomerizes to starting material, the reaction rate being strongly dependent on the hydrogen‐bond‐acceptor basicity of the solvent. The enol is trapped in the presence of acid by protonation at the remaining carbonyl oxygen atom and subsequent electrophilic reaction of the exocylclic methylene group.

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