Syntheses and Reactions of Amino- and Azidophenalenones

Abstract

3-Hydroxyphenalenones 3, synthesized from 1,8-naphthalic anhydride 1 and malonates 2, react by electrophilic halogenation to 2-chlorophenalenediones 4 or 2-iodophenalenone 5. The chloro group of 4 was exchanged against azide by reaction with sodium azide to give 2-azidophenalenediones 6. Nucleophilic chlorination of 3 furnishes 3-chlorophenalenones 7, which were converted to 3-azidophenalenones 8. Staudinger reaction of 8 with triphenylphosphane gave phosphazenes 9 which hydrolyzed to 3-aminophenalenones 10. Amines 10 can also be obtained directly from 3-hydroxyphenalenones 3 and ammonium acetate, or by catalytic hydrogenolysis of azides 8. Nitration of 3-hydroxyphenalenone 3a with nitric acid forms 2-nitrophenalenone 11, which was converted to 3-chloro-2-nitrophenalenone 12. Attempts to introduce the 3-azido group in 12, however, resulted in an exchange of both, the nitro group and the chloro group, to form 2,3-diazidophenalenone 13.2-Amino-3-hydroxyphenalenone 14 cyclizes with carboxylic acid derivatives to oxazolo-phenalenones 15, which were also obtained from 3-azidophenalenone 8a and a carboxylic acid involving an azirine intermediate 16. This allows to move the position of the N-atom. Another cyclization reaction leads via the intermediate oxime 22 of 2-acetylphenalenone 21, which gives an isomer mixture of isoxazolophenalenone 23 as main product and oxazolophenalenone 15 as by-product, because of a parallel reaction via a Beckmann rearrangement.cyclization reactions [8][9][10][11]. In this paper we investigate the synthesis of aminophenalenones and azidophenalenones, their reactivity against electrophilic and nucleophilic reactions and their ability for ring closure reactions to phenaleno-oxazoles and isoxazoles. Synthesis of 3-hydroxyphenalenones 3.Electrophilic halogenation to 4 and 5.