Niobium Pentachloride Activation of Enone Derivatives: Diels- Alder and Conjugate Addition Products

Molecules

Mauricio Gomes Constantino¹  Valdemar Lacerda Júnior² 

[1] id="af1-">Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes 3900, 14040-901 – Ribeirão Preto – SP, Brazil. Phone [phone]. Fax [phone]

关键词: Niobium pentachloride;    Lewis acid;    Diels-Alder reaction;    vinyl chlorides;   

DOI  :  10.3390/70500456

来源: mdpi

【 摘 要 】

Niobium pentachloride has proven to be a powerful activating agent for Diels-Alder or conjugate addition reactions of cycloenones. The Diels-Alder product was obtained only with an unsubstituted enone (cyclohexenone) and the highly reactive diene cyclopentadiene; substituents in the β-position of enones seem to prevent Diels-Alder reaction: oxygenated substituents favor the formation of vinyl chlorides (ethyl ether or dichloromethane as solvents) or enol ethers (ethyl acetate as solvent), while a methyl substituent prevents any kind of transformation with NbCl₅. Less reactive dienes, furan and 2-methylfuran gave the conjugate addition products of the furan ring to the enone system.

【 授权许可】

Unknown   
© 2002 by MDPI (http://www.mdpi.org).