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Construction of Highly Substituted Nitroaromatic Systems by Cyclocondensation. Part I. Synthesis of 4‐nitro‐3‐oxobutyrate
Author(s) -
Duthaler Rudolf O.
Publication year - 1983
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19830660516
Subject(s) - chemistry , acetylacetone , enol , nitro , nitration , yield (engineering) , medicinal chemistry , succinimide , organic chemistry , alkyl , catalysis , materials science , metallurgy
Methyl 4‐nitro‐3‐oxobutyrate ( 1 ) is prepared by substitution of 4‐bromo‐ and 4‐iodo‐3‐oxobutyrate enol ether or enol acetate derivatives with nitrite and deprotection of the keto function ( Schemes 2 and 3 ). A much more convenient access to 1 is, however, the nitration of acetoacetate dianion with alkyl nitrates (Scheme 4) . Compound 1 is stable and storable, and can be handled safely. Its use in cyclocondensations is established by the reaction with acetylacetone (Scheme 5) , affording 4,6‐dimethyl‐3‐nitrosalicylate 48 in 70% yield. The halogen‐substitution method for the synthesis of 1 gives also access to the crystalline ( E )‐enol ether 18 of 1 , as well as to its dimethyl acetal 25 , ( Z )‐enol acetate 32 , and ( E )‐enol acetate 33 . The 3‐substituted 4‐bromobutenoates 15, 16 and 26 have been prepared from 4‐bromo‐3‐oxobutyrate 12 , a useful alternative to existing methods applying N ‐bromo‐succinimide.