Synthesis of some fenchyl-substituted alkenes and enol-ethers containing 3-oxyphenyl substituents by the Barton-Kellogg reaction

• Autor(a) principal: Ciscato,Luiz Francisco M. L.
• Data de Publicação: 2010
• Outros Autores: Bastos,Erick L., Bartoloni,Fernando H., Günther,Wolfgang, Weiss,Dieter, Beckert,Rainer, Baader,Wilhelm Josef
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532010001000014
• topic: Barton-Kellogg olefination; hindered alkenes; diazo compounds; thioketone; fenchone

The synthesis of one fenchyl-substituted alkene and two enol-ethers, containing 3-oxyphenyl substituents by the Barton-Kellogg reaction is described. The tri-substituted aromatic fenchyl-alkene 1a was prepared in 53% yield from thiofenchone and a diazoanisole; whereas enol-ethers 1b and 1c were obtained (95 and 75% yield, respectively) using an inverse approach based on diazofenchone and aromatic thionoesters. A mixture of Z and E isomers was obtained in all cases; isomer attribution and quantification has been carried out by analysis of NMR spectroscopic data assisted by theoretical calculations (E/Z ratio: 1a = 0.72, 1b = 2.2, 1c = 1.8). Reaction proceeds with low stereoselectivity leading to the preferential formation of diastereoisomeric olefins and enol-ethers where the aromatic substituent resides at the side of the two fenchyl methyl groups.