The reaction of safrole derivatives with aluminum chloride: improved procedures for the preparation of catechols or their mono-O-Methylated Derivatives and a mechanistic interpretation

• Autor(a) principal: Amorim,Mauro B. de
• Data de Publicação: 2001
• Outros Autores: Silva,Alcides J. M. da, Costa,Paulo R. R.
• 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=S0103-50532001000300005
• topic: aluminum chloride; 1,3-benzodioxole; safrole; molecular orbitals; MNDO

An improved procedure for the "one-pot" preparation of cathecols from methylenedioxy-ring cleavage reaction of safrole derivatives with aluminum chloride is described. In substrates substituted by conjugated electron-withdrawing groups (carboxyaldehyde or nitro groups) the regioselective formation of the easily isolable chloromethyl ether intermediates was observed. From these intermediates the syntheses of mono-O-methylated phenols (3-hydroxy-4-methoxybenzaldehyde, 2-bromo-4-methoxy-5-hydroxybenzaldehyde, 2-nitro-4-methoxy-5-hydroxybenzaldehyde and 2-methoxy-4-(2-oxoprop-1-yl)-5-nitrophenol) were accomplished. Based on these experimental data and semi-empirical (MNDO) molecular orbital calculations, a mechanistic rationale that explains the observed regioselectivities was also proposed.