Construction of Highly Substituted Nitroaromatic Systems by Cyclocondensation. Part II. Conversion of 4‐nitro‐3‐oxobutyrate to 3‐nitrosalicylates

The base‐catalyzed reaction of 4‐nitro‐3‐oxobutyrate (6) with acetylacetone ( 8 Scheme 3 ), formylacetone ( 13 , Scheme 4 ), formylcyclohexanone ( 31 , Scheme 5 ), 2,4‐dioxopentanoates 39 and 40 (Scheme 6) , and 2,4,6‐heptanetrione ( 2 , Scheme 7 ) affords substituted 3‐nitrosalicylates, products of a double aldol condensation. With unsymmetrical dicarbonyl compounds both regioisomers are formed. High selectivity was found in the case of β‐keto‐aldehydes 13 and 31 with preferred addition of the NO 2 ‐substituted carbon to the aldehyde carbonyl. The major products of these cyclocon‐densations, which are isolated in yields ranging from 20% to 80%, are all new compounds. Less successful are the conversions with β‐alkoxy‐ and β‐chloro‐vinyl ketones ( 23, 25 , and 26 ), and with alkinone 24 , where the condensation products are formed in very low yield (Scheme 4) .