Optically active, bulky tris(oxazolinyl)borato magnesium and calcium compounds for asymmetric hydroamination/cyclization

TitleOptically active, bulky tris(oxazolinyl)borato magnesium and calcium compounds for asymmetric hydroamination/cyclization
Publication TypeJournal Article
Year of Publication2011
AuthorsNeal SR, Ellern A, Sadow AD
Journal TitleJournal of Organometallic Chemistry
Volume696
Pages228-234
Date Published01
Type of ArticleArticle
ISBN Number0022-328X
Accession NumberWOS:000285918100031
Keywords(tris(pyrazolyl)hydroborato)magnesium, Alkaline earth metal, alkyl derivatives, aminoalkenes, catalysis, complexes, hydroamination, intramolecular hydroamination, ligands, organolanthanide-catalyzed hydroamination, oxazoline, POLYMERIZATION, solid angles, unprotected amino olefins
Abstract

The synthesis of the new chiral, pseudo C(3)-symmetric, monoanionic ligand tris(4S-tert-butyl-2-oxazolinyl) phenylborate [To(T)](-) is reported. The steric bulk, tridentate coordination, and anionic charge of [To(T)](-) are suitable for formation of complexes of the type To(T)MX, where one valence is available for reactivity. With this point in mind, we prepared magnesium and calcium To(T) complexes that resist redistribution to (To(T))(2)M compounds. Both To(T)MgMe and To(T)CaC(SiHMe(2))(3) contain tridentate To(T)-coordination to the metal center, as shown by NMR spectroscopy, infrared spectroscopy, and X-ray crystallography. These compounds are active catalysts for the cyclization of three aminoalkenes to pyrrolidines, and provide non-racemic mixtures of pyrrolidines in enantiomeric excesses up to 36%. (C) 2010 Elsevier B.V. All rights reserved.

DOI10.1016/j.jorganchem.2010.08.057
Alternate JournalJ. Organomet. Chem.