hitherto unknown 3,4‐benzotropolones. The 8‐ethoxycarbonylated dimethyl‐3,4‐benzotropolone 50 obtained by this route was dimethylated to give goupiolone A (52). This synthesis encompasses 9 steps from 22, that is, half as many as the only previous synthesis (19 steps). A variant of our route afforded the 1,8‐dibromide 54. Coupling with excess phenylboronic acid and ketal hydrolysis provided the diphenylated
Syntheses of 3,4-Benzotropolones by Ring-Closing Metatheses
作者:Deniz Arican、Reinhard Brückner
DOI:10.1021/ol400510j
日期:2013.6.7
Ortho-lithiated styrenes or ortho-lithiated benzaldehyde dimethylacetals were added to 2,2-dimethoxypent-4-enals 7. The resulting alcohols were carried on to the aromatic dienones 10. These were ring-closed by olefin metathesis. Hydrolysis of the dimethylketal moiety and enolization provided the 3,4-benzotropolones 5. Overall, this access comprises 4–6 steps and totaled a 22–81% yield.