Diastereoselective Domino Reactions of Chiral 2-Substituted 1-(2′,2′,3′,3′-Tetramethylcyclopropyl)-alkan-1-ols under Friedel−Crafts Conditions
作者:Daniel Stadler、Thorsten Bach
DOI:10.1021/jo900445c
日期:2009.7.3
shift to allylic cations I. The latter cations are eventually attacked by the arene nucleophile. The diastereoselectivity of this process is good (anti-preference for Ph, CN, PO(OEt)2) to excellent (syn-preference for tBu). The esters 7, carrying a methoxycarbonyl group in 2-position, yielded under the same reaction conditions products 25 and 26, which are formed by an intermolecular Friedel−Crafts reaction
2-取代的1-(2',2',3',3'-四甲基环丙基)-alkan -1-醇3 - 7通过羰除了四甲基环锂到相应的醛或通过添加相应的被取代的碳负离子的制备到四甲基环丙基甲醛16。在布朗斯台德酸性条件下(HBF 4 ·OEt 2),该醇在与2-甲基噻吩(8)和N-甲苯磺酰基(9)的Friedel-Crafts烷基化反应中充当底物。所述链烷醇3 - 6携带基团吨卜中,Ph,CN,PO(OET)2在2-位输送的重排的取代产物17 - 20在非常好的化学产率(9个实施例中,81-97%)。产物大概是通过四甲基环丙基取代的阳离子的开环形成的,该阳离子通过Wagner-Meerwein转变为烯丙基阳离子I重排。后者阳离子最终被芳烃亲核试剂攻击。该方法的非对映选择性良好(对Ph,CN,PO(OEt)2的反偏好)至优异(对t Bu的顺偏好)。在相同反应条件下产生在2位带有甲氧基羰基的酯7,产物25和通过分