H. C. Brown Laboratories of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, IN 47907-2084, USA.
Chem Asian J. 2013 Aug;8(8):1829-35. doi: 10.1002/asia.201300311. Epub 2013 May 13.
A highly enantioselective and widely applicable method for the synthesis of various chiral 2-alkyl-1-alkanols, especially those of feeble chirality, has been developed. It consists of zirconium-catalyzed asymmetric carboalumination of alkenes (ZACA), lipase-catalyzed acetylation, and palladium- or copper-catalyzed cross-coupling. By virtue of the high selectivity factor (E) associated with iodine, either (S)- or (R)-enantiomer of 3-iodo-2-alkyl-1-alkanols (1), prepared by ZACA reaction of allyl alcohol, can be readily purified to the level of ≥99% ee by lipase-catalyzed acetylation. A variety of chiral tertiary alkyl-containing alcohols, including those that have been otherwise difficult to prepare, can now be synthesized in high enantiomeric purity by Pd- or Cu-catalyzed cross-coupling of (S)-1 or (R)-2 for introduction of various primary, secondary, and tertiary carbon groups with retention of all carbon skeletal features. These chiral tertiary alkyl-containing alcohols can be further converted into the corresponding acids with full retention of the stereochemistry. The synthetic utility of this method has been demonstrated in the highly enantioselective (≥99% ee) and efficient syntheses of (R)-2-methyl-1-butanol and (R)- and (S)-arundic acids.
一种高对映选择性和广泛适用的合成各种手性 2-烷基-1-烷醇的方法,特别是那些弱手性的 2-烷基-1-烷醇的方法已经被开发出来。该方法由锆催化的烯烃不对称碳铝化反应(ZACA)、脂肪酶催化的乙酰化反应和钯或铜催化的交叉偶联反应组成。由于碘的高选择性因子(E),通过 ZACA 反应由烯丙醇制备的 3-碘-2-烷基-1-烷醇(1)的(S)-或(R)-对映异构体可以通过脂肪酶催化的乙酰化反应很容易地被纯化为≥99%ee 的水平。各种含有手性叔烷基的醇,包括那些以前难以制备的醇,现在可以通过 Pd 或 Cu 催化的(S)-1 或(R)-2 的交叉偶联反应以高对映体纯度合成,用于引入各种伯、仲和叔碳原子,同时保留所有碳骨架特征。这些含有手性叔烷基的醇可以进一步转化为相应的酸,同时保留立体化学的全部特征。该方法的合成实用性已在(R)-2-甲基-1-丁醇和(R)-和(S)-阿仑酸的高对映选择性(≥99%ee)和高效合成中得到了证明。