Chiral Synthesis via Organoboranes. 47. Efficient Synthesis of Unsymmetrical Ketones and Enantiomerically Pure Spiroketals Using (±)-Isopinocampheyldichloroborane
作者:Herbert C. Brown、Shekhar V. Kulkarni、Uday S. Racherla、Ulhas P. Dhokte
DOI:10.1021/jo980989w
日期:1998.10.1
intermediate was readily converted into the unsymmetrical ketones, R(1)COR(2), in high yields and purity, by an established method. This methodology was successfully applied to the synthesis of enantiomerically pure spiroketals using optically pure TBS ether protected homoallylic alcohols as the alkenes for stepwise hydroboration.
现成的且稳定的(+/-)-异樟脑基二氯硼烷[(+/-)-IpcBCl(2)]使用原位还原-氢硼化方案方便地用于两个不同烯烃的逐步氢硼化,从而得到混合的三烷基硼烷IpcBR(1 R(2)。通过用醛RCHO处理从这些三烷基硼烷中方便地消除α-pine烯,提供了硼酸酯R(1)R(2)BOCH(2)R。通过建立的方法,该中间体很容易以高收率和高纯度转化为不对称酮R(1)COR(2)。该方法已成功地应用于光学纯的TBS醚保护的均烯丙基醇作为烯烃进行逐步硼氢化的对映体纯螺环酮的合成。