Regiospecific electroacetoxylation of 4-methylphenyl acetate to form 4-acetoxybenzyl acetate. A significant procedure for vanillin synthesis involving novel etherification methods of aryl bromides

Sigeru Torii, Hideo Tanaka, Takasi Siroi, Mitsuo Akada

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28 Citations (Scopus)

Abstract

Electroacetoxylation of 4-methylphenyl acetate (1) was carried out in AcOH-t-BuOH (9:1 v/v) in in the presence of copper(II) acetate by using carbon electrodes to give the side-chain-oxidized products in 88% selectivity (90% conversion), i.e., 4-acetoxybenzyl acetate (2a, 69%), 4-acetoxybenzaldehyde (4a, 8%), and 4-acetoxybenzylidene diacetate (3, 3%). The electrolysis products 2a, 3, and 4a, either by platinum oxide catalyzed oxygen oxidation or by acid-catalyzed hydrolysis, were smoothly converted to 4-hydroxybenzaldehyde (4b) whose bromination provided 3-bromo-4-hydroxybenzaldehyde (5a, 90%) as well as 3,5-dibromo-4-hydroxybenzaldehyde (5b, 4.5%). Treatment of 5a with either ROH-NaOH-CaO/DMF-CuCl2 or ROH-BaO-DMF-CuCl2 resulted in vanillin (6a, 94%) and ethyl vanillin (6b, 93%), respectively. On the other hand, acid-catalyzed hydrolysis of 2a gave 4-hydroxybenzyl alcohol (11, 89%), and acid-catalyzed alcoholysis of 2a furnished 4-hydroxybenzyl ethers 8a (100%) and 8b (99%). The oxygen oxidation of both 8 and 11 can produce 4b in good yield. 4-Hydroxy-3-methoxy(or ethoxy)benzyl ether (10), another key precursor for the vanillin synthesis, was prepared from both 8 and 11 by bromination followed by etherification with ROH-BaO-DMF-CuCl2 in good yield.

Original languageEnglish
Pages (from-to)3305-3310
Number of pages6
JournalJournal of Organic Chemistry
Volume44
Issue number19
Publication statusPublished - 1979

ASJC Scopus subject areas

  • Organic Chemistry

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