TY - JOUR
T1 - Regiospecific Electroacetoxylation of 4-MethylphenyI Acetate to Form 4-Acetoxybenzyl Acetate. A Significant Procedure for Vanillin Synthesis Involving Novel Etherification Methods of Aryl Bromides
AU - Torii, Sigeru
AU - Tanaka, Hideo
AU - Siroi, Takasi
AU - Akada, Mitsuo
PY - 1979
Y1 - 1979
N2 - Electroacetoxylation of 4-methylphenyl acetate (1) was carried out in AcOH-t-BuOH (9:1 v/v) m m 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 5awith either ROH-NaOH-CaO/DMF-CuCl2 or ROH-BaO-DMF-CuCl2 resulted in vanillin (6a, 94%) and ethylvanillin (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.
AB - Electroacetoxylation of 4-methylphenyl acetate (1) was carried out in AcOH-t-BuOH (9:1 v/v) m m 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 5awith either ROH-NaOH-CaO/DMF-CuCl2 or ROH-BaO-DMF-CuCl2 resulted in vanillin (6a, 94%) and ethylvanillin (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.
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U2 - 10.1021/jo01333a006
DO - 10.1021/jo01333a006
M3 - Article
AN - SCOPUS:0041444271
VL - 44
SP - 3305
EP - 3310
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 19
ER -