Desymmetrizing Intramolecular Arylations

As mentioned above, the enantioselective desymmetrization of prochiral, as well as meso compounds, by using a Mizoroki-Heck coupling represents another pos-sibiUty to effect asymmetric transformations [81-84]. Therefore, the plane of symmetry in these precursors must be broken by differentiation of enantiotopic alkene-containing groups with a chiral palladium complex. 

133a 100% oonv 96% ee 133b 5% oonv 133c 25% oonv 75% ee 

JOSIPHOS (137) gave 138 in 92% yield and 84% ee. As in the preceding case, the leaving group (iodide, bromide, triflate or nonaflate) had almost no effect on stereoinduction, but the yields were lower. 

Furthermore, this oxygen-directed, intramolecular Mizoroki-Heck methodology found a first application in the synthesis of an AB synthon of anthracyclines [84bj. 

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Haseltine has described an enantioselective formal synthesis of pancratistatin in which the stereocontrol is driven by the aeetonide of conduritol A. The enantioselective hydrolysis (desymmetrization) of this compound was achieved with a lipase, and the aryl-cyclohexane ring bond was formed through an intramolecular cyclization of the activated benzene ring with an allylic triflate (278). Plumet reported a total synthesis of (-l-)-7-deoxypaneratistatin based on the conjugate addition of an aryl-lithium species to a bicyclic conjugated sulfone derived from furan, which enabled the efficient installation of the six stereogenic centers of the cyclohexane ring (279) (Scheme 13). 

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