Synthesis of 10‐Aryl‐10H‐naphtho[1,8a,8‐fg]indazol‐7‐ones

Abstract

Dedicated to Professor Thomas Kappe on the occasion of his 70th birthday3 -H y d r o x y -2 -[ 1 -( a r y l h y d r a z o n o ) e t h y l ] -1H-phenalen-1-ones 3, obtained from 2-acetyl-3-hydroxy-1H-phenalen-1-one (1) and arylhydrazines 2, cyclize under acidic conditions to 8-methyl-10-aryl-10H-naphtho-[1,8a,8-fg]indazol-7-ones 4. Indazoles 4 are also obtained from 2-acetyl-3-hydroxy-1H-phenalen-1-one (1) and arylhydrazines 2 in a one-pot reaction. 2-Acetyl-3-azido-1H-phenalen-1-one (6) does not give 8-methyl-9-arylamino-9H-naphtho [1,8a,8-fg]indazol-7-ones via azide decomposition but gives again by nucleophilic replacement of the azide moiety in 6 the indazole 4. J. Heterocyclic Chem., 40, 753(2003).Indazole derivatives are of great interest because of their pharmaceutical activity, use in agrochemistry, in dye chemistry and in photographic processes [2]. Whereas the basic ring system of indazole is investigated thoroughly, polyfused derivatives are rarely described. In the course of our investigations of ring closure reactions of phenalene derivatives [3-5] we focused our interest on the synthesis of indazoles of type A (typus of a 1H-indazole) and of type B (typus of a 2H-indazole). In the literature, only one example of such an indazole of type A is described as a follow-up product in the ring enlargement of acenaphthenequinone [6]. Scheme 1We started our synthesis program with a 2-acyl-1-hydrazinoarene synthon, which should give in the cyclization step the formation of one new N-C bond. As the first step in this reaction the hydrazinolysis of 2-acetyl-3-hydroxy-1H-phenalen-1-one (1) was planned. 2-Acetyl-3-hydroxy-1H-phenalen-1-one (1) was obtained in a 2-step reaction from phenalene-1,3-dione by cyclocondensation with diethyl malonate, followed by a ring-opening reaction in sodium hydroxide solution and subsequent spontaneous decarboxylation upon acidification as described recently [5]. Attempts to obtain 2-acetyl-3-hydroxy-1H-phenalen-1-one (1) in a one step reaction by direct acetylation of phenalene-1,3-dione using acetic acid with acid catalysts as described in several heterocyclic systems [7] was not successful.The reaction of 2-acetyl-3-hydroxy-1H-phenalen-1-one (1) with arylhydrazines 2 was performed either in dimethylformamide without catalyst in the case of phenylhydrazine (2a) or with glacial acetic acid and sulfuric acid as catalyst in the case of 4-nitrophenylhydrazine (2b). In both cases 3-hydroxy-2-[1-(arylhydrazono)ethyl]-1H-phenalen-1-ones 3 were obtained in 48 and 97% yield, respectively.Because of the high reactivity of 3a, in all experiments, traces of the follow-up ring closed compound 4 a w e r e

Syntheses and Reactions of Amino- and Azidophenalenones

“…3-Chloro-2-nitrophenalen-1-one (12): A mixture of 3-hydroxy-2-nitrophenalen-1-one (11) (2.08 g, 8.3 mmol), phosphoryl chloride (30 mL) and triethylamine (1.26 mL, 9 mmol) was heated for 1 hour under reflux, cooled to room temperature and poured onto ice/water (150 mL) under stirring. A greenish precipitate was formed, which was stirred for 1 hour at 20 °C and then filtered by suction.…”

“…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.…”

“…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.…”

Five‐Membered Heterocycles: 1,2‐Azoles. Part 1. Pyrazoles

“…The reaction needs a slightly acidic medium to catalyze the conversion of the ketone into the hydrazone and it is imperative the use of a Dean-Stark apparatus to eliminate the water, to avoid mesylate hydrolysis to the corresponding phenol, which does not cyclize to indazoles under these reaction conditions. and hexahydro-1H-and 2H-indazole derivatives are also obtained from the reaction of appropriate chalcone-type compounds or b-diketones with hydrazine derivatives [283,284,[286][287][288].…”