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Diazotization of Methyl 3‐Amino‐7‐Isopropyl‐2‐Methoxyazulene‐1‐Carboxylate and its 5‐Isopropyl Isomer‐ a Convenient Synthesis of 1,2‐Azulenequinone Derivatives
Author(s) -
Huang TianChyuan,
Lin YunShan,
Lin ShihJue,
Chu ShuFan
Publication year - 1996
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.199600007
Subject(s) - chemistry , isopropyl , carboxylate , nitration , yield (engineering) , trifluoroacetic acid , medicinal chemistry , acetic acid , protonation , organic chemistry , ion , materials science , metallurgy
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.