While imines are frequently used substrates in asymmetric Bronsted acid catalysis, their corresponding salts are generally considered unsuitable reaction partners. Such processes are challenging because they require the successful competition of a catalytic amount of a chiral anion with a stoichiometric amount of an achiral one. We now show that enantiopure disulfonimides enable the asymmetric reduction of N–H imine hydrochloride salts using Hantzsch esters as hydrogen source. Our scalable reaction delivers crystalline primary amine salts in great efficiency and enantioselectivity and the discovery suggests potential of this approach in other Bronsted acid catalyzed transformations of achiral iminium salts. Kinetic studies and acidity data suggest a bifunctional catalytic activation mode.

中文翻译：

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手性布朗斯台德酸催化已质子化底物的不对称加成：高对映选择性二磺酰亚胺催化的 NH-亚胺盐酸盐的 Hantzsch 酯还原

虽然亚胺是不对称布朗斯台德酸催化中经常使用的底物，但它们相应的盐通常被认为是不合适的反应伙伴。这些过程具有挑战性，因为它们需要催化量的手性阴离子与化学计量量的非手性阴离子成功竞争。我们现在表明，使用 Hantzsch 酯作为氢源，对映体纯二磺酰亚胺能够不对称还原 N-H 亚胺盐酸盐。我们的可扩展反应以高效率和对映选择性提供结晶伯胺盐，这一发现表明这种方法在其他布朗斯台德酸催化的非手性亚胺盐转化中具有潜力。动力学研究和酸度数据表明双功能催化活化模式。