Steigerwald Daniel C, Soltanzadeh Bardia, Sarkar Aritra, Morgenstern Cecilia C, Staples Richard J, Borhan Babak
Michigan State University, Department of Chemistry East Lansing MI 48824 USA
Chem Sci. 2020 Dec 7;12(5):1834-1842. doi: 10.1039/d0sc05224h.
Intermolecular asymmetric haloamination reactions are challenging due to the inherently high halenium affinity (HalA) of the nitrogen atom, which often leads to -halogenated products as a kinetic trap. To circumvent this issue, acetonitrile, possessing a low HalA, was used as the nucleophile in the catalytic asymmetric Ritter-type chloroamidation of allyl-amides. This method is compatible with and alkenes with both alkyl and aromatic substitution. Mild acidic workup reveals the 1,2-chloroamide products with enantiomeric excess greater than 95% for many examples. We also report the successful use of the sulfonamide chlorenium reagent dichloramine-T in this chlorenium-initiated catalytic asymmetric Ritter-type reaction. Facile modifications lead to chiral imidazoline, guanidine, and orthogonally protected 1,2,3 chiral tri-amines.
分子间不对称卤胺化反应具有挑战性,因为氮原子固有的高卤鎓亲和力(HalA),这常常导致生成α-卤代产物作为动力学陷阱。为了规避这个问题,具有低HalA的乙腈被用作烯丙基酰胺催化不对称里特型氯酰胺化反应中的亲核试剂。该方法适用于具有烷基和芳基取代的烯烃和乙烯。温和的酸性后处理揭示了许多实例中对映体过量大于95%的1,2-氯酰胺产物。我们还报道了在这种由氯鎓引发的催化不对称里特型反应中成功使用磺酰胺氯鎓试剂二氯胺-T。简便的修饰可得到手性咪唑啉、胍和正交保护的1,2,3-手性三胺。