Fernandez E, Maeda K, Hooper MW, Brown JM
The Dyson Perrins Laboratory, Oxford, UK.
Chemistry. 2000 May 15;6(10):1840-6. doi: 10.1002/(sici)1521-3765(20000515)6:10<1840::aid-chem1840>3.0.co;2-6.
Catecholboronate esters formed by asymmetric hydroboration of arylalkenes are not directly converted to amines by reaction with hydroxylamine-O-sulfonic acid. Prior conversion to a trialkylborane by reaction with ZnEt2 or MeMgCl permits a subsequent amination reaction to occur with essentially complete retention of configuration, leading to a range of primary alpha-arylalkylamines in up to 97% enantiomeric excess (ee). Secondary, but not tertiary amines may be formed by a related pathway when in situ generated alkylchloramines are employed as the aminating agent. The catalytic asymmetric hydroboration, beta-alkylation and amination steps may be combined in a single stage. Overall, this provides a practical procedure for the synthesis of enantiomerically enriched arylamines, exemplified inter alia by the synthesis of (S)-1,2,3,4-tetrahydro-1-naphthylamine in 95-97% ee and of (R)-N-(cyclohexyl)-1'-(4-methoxyphenyl)ethylamine in 93% ee.
芳基烯烃不对称硼氢化形成的儿茶酚硼酸酯不能通过与羟胺 - O - 磺酸反应直接转化为胺。通过与ZnEt2或MeMgCl反应预先转化为三烷基硼烷，使得随后的胺化反应能够发生，且构型基本完全保留，从而得到一系列对映体过量高达97%的伯α - 芳基烷基胺。当使用原位生成的烷基氯胺作为胺化剂时，仲胺而非叔胺可通过相关途径形成。催化不对称硼氢化、β - 烷基化和胺化步骤可在一个阶段中结合。总体而言，这为对映体富集芳基胺的合成提供了一种实用方法，例如以95 - 97% ee的(S)-1,2,3,4 - 四氢 - 1 - 萘胺和93% ee的(R)-N-(环己基)-1'-(4 - 甲氧基苯基)乙胺的合成为例。
