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Transformation of 5,6,7,8-Tetrahydro-2H-1-benzopyran-2,8-diones with Hydrazines and Hydrazoic Acid: Synthesis of 8-Hydrazono-5,6,7,8-tetrahydro-2-oxo-2H-1-benzopyrans, Pyrano[2,3-c]azepines and Pyrido[2,3-c]azepines

2000; Elsevier BV; Volume: 53; Issue: 5 Linguagem: Inglês

10.3987/com-00-8878

1881-0942

Marijan Kočevar, Polonca Trebše, Lidija Vraničar, Irena Mušič, Slovenko Polanc, William C. Stevens,

Synthesis and Biological Activity

6,7,benzamide (1a) reacts with nitrogen-containing nucleophiles (2) (hydrazines and hydroxylamine) to give the corresponding 8-hydrazono derivatives (3a-i) and the related hydroxyimino derivative (3j).The action of hydrazoic acid on 1a-b or 3a-b and 3e resulted in the formation of pyrano[2,3-c]azepines (4a-b).The pyranoazepine (4a) can be debenzoylated to 4b or transformed into pyrido[2,3c]azepines (5a-b).2H-Pyran-2-ones and fused pyran-2-ones are important synthons and building blocks in organic synthesis. 1Fused pyran-2-ones, such as 5-, 6-, 7-, or 8-oxo substituted 5,6,7,8-tetrahydro-2H-1benzopyran-2-ones possess several reactive centers.For example, nucleophiles might react either with the lactone ring or with the keto group.Previous results have shown that N- (5,6,7,8-tetrahydro-2,5-dioxo-2H-1-benzopyran-3-yl)benzamides gave the corresponding quinolines 2a-c when reacted with nitrogencontaining nucleophiles, such as ammonia, hydroxylamine, aniline, amino acids, hydrazine and N,Ndimethylhydrazine. On the other hand, hydrazides, phenylhydrazines and heterocyclic hydrazines converted benzopyran-2,5-diones selectively into 5-hydrazonobenzopyrans.2c-f These reactions were # Dedicated with deep respect to Professor Richard Neidlein on the ocassion of his 70 th birthday.