A Convenient Entry to 3-Methylidenechroman-2-ones and 2-Methylidenedihydrobenzochromen-3-ones
作者:Tomasz Janecki、Jakub Modranka、Anna Albrecht
DOI:10.1055/s-0030-1259046
日期:2010.12
A simple and versatile synthesis of 3-methylidenechroman-2-ones and 2-methylidenedihydrobenzochromen-3-ones has been developed. The reaction of phenols or naphthols with 3-methoxy-2-diethoxyphosphorylacrylate gave intermediate 3-diethoxyphosphorylchromen-2-ones or 2-diethoxyphosphorylbenzo-chromen-3-ones, respectively. These compounds were employed as Michael acceptors in the reaction with Grignard reagents to yield 4-substituted 3-diethoxyphosphorylchroman-2-ones or 1-substituted 2-diethoxyphosphoryldihydrobenzochromen-3-ones. The obtained adducts were next used as Horner-Wadsworth-Emmons reagents for the olefination of formaldehyde to give the final products.
The phosphonyl radical generated from the reaction of manganese(III) acetate with diethyl phosphonate selectively adds to the 3-position of flavones and coumarins to afford phosphonylated products in moderate to good yields. manganeseacetate - phosphonylation - flavones - coumarins - dialkyl phosphonate - freeradical