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Highly Enantioselective Zirconium-Catalyzed Cyclization of Aminoalkenes

TitleHighly Enantioselective Zirconium-Catalyzed Cyclization of Aminoalkenes
Publication TypeJournal Article
Year of Publication2013
AuthorsManna, K, Everett, WC, Schoendorff, G, Ellern, A, Windus, TL, Sadow, AD
JournalJournal of the American Chemical Society
Volume135
Pagination7235-7250
Date Published05
Type of ArticleArticle
ISBN Number0002-7863
Accession NumberWOS:000319250200026
Keywords-diamido ligands, alkene hydroamination, alkenes, asymmetric intramolecular hydroamination, ate complexes, h bond formation, hydroamination, intermolecular, kinetic resolution, sigma-insertive mechanism, substituted, unactivated, unprotected amino olefins
Abstract

((D))(obs) = 3.3 +/- 0.3) and from initial rate analysis (k(2)((H))/k(2)((D)) = 2.3 +/- 0.4) indicate that a N-H bond is broken in the turnover-limiting and irreversible step of the catalytic cycle. Asymmetric hydroamination/cyclization of N-deutero-aminoalkenes provides products with higher optical purities than obtained with N-proteo-aminoalkenes. Transition state theory, applied to the rate constant k(2) that characterizes the irreversible step, provides activation parameters consistent with a highly organized transition state (Delta S-double dagger = -43(7) cal.mol(-1) K-1) and a remarkably low enthalpic barrier (Delta H-double dagger = 6.7(2) kcal.mol(-1)). A six-centered, concerted transition state for C-N and C-H bond formation and N-H bond cleavage involving two amidoalkene ligands is proposed as most consistent with the current data.

DOI10.1021/ja4000189
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3D Catalysis

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Chemical Physics