Departamento de Química Orgánica, Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Spain.
Chemistry. 2011 Feb 25;17(9):2734-41. doi: 10.1002/chem.201001124. Epub 2011 Jan 30.
Pd-catalyzed bicyclization of 1-ene-6,11-diynes with bis(pinacolato)diboron smoothly affords synthetically useful homoallylic alkylboronates under mild conditions, avoiding the use of highly nucleophilic or basic reagents. One C-B bond and two new C-C bonds are created, and two new stereogenic centers are stereospecifically formed in a single tandem operation. The obtained products suggest a cascade reaction in which the last step is the transmetalation of bis(pinacolato)diboron, this being faster than a possible β-hydride elimination process. The reaction is general and has been applied to enediynes with different substituents on the alkene unit, the bridging groups, and the alkyne moiety. The bicyclized alkylboronates thus obtained can be functionalized by oxidation to alcohols, formation of trifluoroborate salts, or by Suzuki coupling reactions.
钯催化的 1-烯-6,11-二炔与双(频哪醇)二硼的双环化反应在温和条件下顺利进行，避免了使用高亲核性或碱性试剂。在单一串联反应中，形成了一个 C-B 键和两个新的 C-C 键，并且两个新的手性中心被立体特异性地形成。得到的产物表明存在级联反应，其中最后一步是双(频哪醇)二硼的转金属化，这比可能的β-氢消除过程更快。该反应具有普遍性，并已应用于具有不同取代基的烯炔、桥连基团和炔基部分的烯二炔。由此得到的双环化烷基硼酸酯可以通过氧化成醇、形成三氟硼酸盐盐或通过铃木偶联反应进行官能化。
