(<i>R</i>)-1,1′-Binaphthyl-2-<i>bis</i>(pentafluorophenyl)borane Lewis Acids
作者:Warren E. Piers、Darryl J. Morrison、Masood Parvez
DOI:10.1055/s-2004-832824
日期:——
A practical and high yielding synthetic route was developed for the preparation of optically pure (R)-(+)-2-bis(pentafluorophenyl)boryl-, (R)-(+)-1a,b, and (R)-2-difluoroboryl-1,1′-binaphthyls, (R)-5a,b. Chiral boranes (R)-1a and (R)-5a are active catalysts for the allylstannation of aromatic aldehydes although enantioselectivities for R products were low. A structural investigation of the adduct (±)-1a·o-anisaldehyde suggested that substituents in the 2′-position of the binaphthyl backbone could increase enantiofacial discrimination. Consistent with this structural study, the 2′-Me derivative (R)-1b gave slightly higher enantioselectivities and opposite configuration S of homoallylic alcohol products.
为制备光学纯的(R)-(+)-2-双(五氟苯基)硼烷,(R)-(+)-1a,b 和(R)-2-二氟硼烷-1,1′-联萘,(R)-5a,b 开发了一条实用的高产合成路线。手性硼烷 (R)-1a 和 (R)-5a 是芳香醛烯丙基锡化反应的活性催化剂,但 R 产物的对映选择性较低。对加合物 (±)-1a-o-anisaldehyde 的结构研究表明,二萘基骨架 2′ 位上的取代基可以提高对映选择性。与这一结构研究相一致,2′-Me 衍生物 (R)-1b 的对映体选择性略高,同烯丙基醇产物的构型 S 相反。