Quinine Synthesis Studies: A Radical−Ionic Annulation via Mn-Mediated Addition to Chiral <i>N</i>-Acylhydrazones
作者:Chandra Sekhar Korapala、Jun Qin、Gregory K. Friestad
DOI:10.1021/ol7017938
日期:2007.10.1
A radical-ionic annulation approach to functionalized perhydroisoquinolines involving Mn-mediated coupling of alkyl iodides and chiral N-acylhydrazones was achieved using only 1.25 equiv of the alkyl iodide. Application of this reaction to alkene-containing substrates en route to quinine offered modest yields, decreasing on scaleup. Control experiments revealed that the alkene interfered with the coupling reaction. A revised approach involving prior oxidation of the alkene offered 93% yield in the Mn-mediated coupling, with the adduct obtained as a single diastereomer.
Scope of Stereoselective Mn-Mediated Radical Addition to Chiral Hydrazones and Application in a Formal Synthesis of Quinine
作者:Gregory K. Friestad、An Ji、Jonas Baltrusaitis、Chandra Sekhar Korapala、Jun Qin
DOI:10.1021/jo2026349
日期:2012.4.6
favored an undesired azabicyclo[3.2.1]octane ring system, an outcome that was found to be consistent with transition state calculations at the B3LYP/6-31G(d) level. Group differentiation at an earlier stage enabled an alternative regioconvergent pathway; this furnished the desired azabicyclo[2.2.2]octane ring system and afforded quincorine (21b), completing a formal synthesis of quinine.