Tian-Chyuan Huang, Yun-Shan Lin, Shih-Jue Lin
Feb 1, 1996
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0
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Journal
Journal of The Chinese Chemical Society
Abstract
Methyl 3-amino-2-methoxy-7-isopropylazulene-l-carboxylate(8a) and its 5-isopropyl isomer (8b) were synthesized by reduction of the 3-nitro derivatives (7a,b) with zinc/acetic acid in excellent yields. 7a and 7b were prepared by nitration and methylation of methyl 7-isopropyl-2-hydroxyazulene-l-carboxylate (5a) and methyl 5-isopropyl-2-hydroxyazulene-l-carboxylate (5b), respectively. Diazotization of 8a with sodium nitrite in trifluoroacetic acid at 0 °C gave methyl 5-isopropyl-1,2-azulenequinone-3-carboxylate (9a) in 91% yield. Similar reaction of 8b gave the corresponding methyl 7-isopropyl-1,2-azulenequinone-3-carboxylate (9b) in 93% yield. No evidence for the formation of l-diazo-1,2-azulenequinones was obtained.