Photolysis of anthranils

Photolysis of anthranils (506) in methanol or amines gives 2-methoxy- or 2-amino-3//-azepines (507) by ring expansion of intermediate nitrenes (8iAHC(28)23l). Photolysis of 2-alkylindazoles... 

Treatment of phthalic acid (145) with sodium azide under acidic conditions has been reported" to give various products anthranilic acid (147) and a trace of o-phenylenediamine (148) in concentrated sulfuric acid and anthranilazide (149) and benzimidazol-2-one (150) in 90% sulfuric acid. Analogously, phthalic anhydride (146) gives the following products anthranilic acid (147), benzimidazol-2-one (150) and some 3,l-benzoxazine-2,4(l//)-dione (isatoic anhydride) (151) in sulfuric acid and benzimidazol-2-one (150) in acetic acid. A recent report" has revealed that Ae Schmidt reaction of phthalic acid (145) in 90-98% sulfuric acid gives anthranilic acid (147) and anthranilazide (149) (major products) by a process thought to involve 3,l-benzoxazine-2,4(l//)-dione (151) as an intermediate. Benzimidazol-2-one (150) is produced in this reaction by a secondary process from anthranilazide (149). Photolysis of (149) also produces (150). 

Photolysis of 3-(pentafluorophenyl)anthranil in light petrol yields 2 -amino-2,3,4,5,6-pentafluorodiphenyl ketone.143... 

Photolysis of 2-alkylindazoles (aza analogs of anthranils) in aqueous media gives either azepinones (7) or 2-amino-5-hydroxyacetophenones (8) depending upon the pH — a nitrene nitrenium ion equilibrium is thought to be involved. ... 

Reactions of piperazine-2,5-diones with phosphorus pentachloride and phosphorus pentabromide have been described in Sections V.ID and V.IF, respectively. Aromatic aldehydes condense with 3-methylpiperazine-2,5-dione in the presence of acetic anhydride to form mainly mono-A -acetyl derivatives of trans-3-arylidene-6-methylpiperazine-2,5-diones (e.g., 96, R = Ac) (1066). In these products the acetyl group was shown to be attached to position 1 and the 4,5-amide group was found to be sterically hindered. Photolysis formed the cis isomers. Both isomers were deacetylated with methanolic potassium hydroxide (1066). Condensation of 1,4-diacetylpiperazine-2,5-diones with aldehydes has been applied to the synthesis of unsymmetrical 3,6-diarylidenepiperazine-2,5-diones and the reaction has been extended to l,4-diacetyl-3,6-dimethylpiperazine-2,5-diones (1624). Treatment of (96, R = H) with triethyloxonium tetrafluoroborate in dichloromethane gave the monoimino ether, 5-benzylidene-6-ethoxy-3-hydroxy-2-methyl-2,5-dihydropyrazine (97) (1066). l-Methylpiperazine-2,5-dione similarly treated gave 5-ethoxy-l-methyl-2-oxo-l,2,3,6-tetrahydropyrazine (which was condensed with anthranilic acid at 150° to 2-methyl-l,2-dihydropyrazino[2,l-fi]quinazoline-3(4/0.6-dione (98) (1625), and l,4-dimethylpiperazine-2,5-dione gave 5-ethoxy-l,4-dimethyl-2-oxo-1,2,3,4-tetrahydropyrazine and 5,5-diethoxy-l,4-dimethylpiperazin-2-one (1626). 

Photodecomposition of o-azidoacetophenone appears to be exclusively via the singlet nitrene, and in nucleophilic solvents (methanol and piperidine) produces 3H-azepines (see Section III,C,7) rather than anthranils.197 Surprisingly, however, and in contrast to other o-azidoamides which on photolysis in methanol yield 2-methoxy-3H-azepine-3-carboxyamides,198... 

Phenyl azide has been claimed" to undergo expansion to 49 in 10% yield on photolysis in methanol, a very weak base. This reaction is much more facile when the azide bears on an ortho substituent containing a carbonyl group. In this case, stabilization of the singlet nitrene (and suppression of intersystem crossing to triplet) can be envisaged by formation of an intermediate anthranil. These are known to give azepines on irradiation in nucleophilic solvents ... 

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