Sequential directed ortho metalation-boronic acid cross-coupling reactions. A general regiospecific route to oxygenated dibenzo[b,d]pyran-6-ones related to ellagic acid
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A general regiospecific synthesis of dibenzo[ b,d]pyran-6-one derivatives la,c and 8a-i related to ellagic acid is described (Scheme I, Table I). The sequence involves directed ortho metalation-boronation of benzamides 4 to give the arylboronic acids 5, which, upon palladium-catalyzed cross-coupling with alkoxybromobenzenes 6 leads to the biphenylamides 7. BBr3 demethylation followed by acid-catalyzed cyclization affords pyranone 8. In this manner, the naturally occurring dibenzopyranones la, autumnariol (IC), and the heterocyclic analogue 13 (Scheme 111) were efficiently prepared.
Research Subject Categories::NATURAL SCIENCES::Chemistry::Organic chemistry , cross-coupling reactions , dibenzo[b,d]pyran-6-ones , ellagic acid
Alo, B. I., Kandil, A., Patil, P. A., Sharp, M. J., Siddiqui, M. A., Snieckus, V., & Josephy, P. D. (1991). Sequential directed ortho metalation-boronic acid cross-coupling reactions. A general regiospecific route to oxygenated dibenzo [b, d] pyran-6-ones related to ellagic acid. The Journal of Organic Chemistry, 56(12), 3763-3768.