Concerted C−N and C−H Bond Formation in a Magnesium-Catalyzed Hydroamination

Coordinatively saturated ToMMgMe (1; ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) is an active precatalyst for intramolecular hydroamination/cyclization at 50 °C. The empirical rate law of −d[substrate]/dt = k′obs[Mg]1[substrate]1 and Michaelis−Menten-type kinetics are consistent with a mechan...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2010-12, Vol.132 (50), p.17680-17683
Main Authors: Dunne, James F, Fulton, D. Bruce, Ellern, Arkady, Sadow, Aaron D
Format: Article
Language:English
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Summary:Coordinatively saturated ToMMgMe (1; ToM = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) is an active precatalyst for intramolecular hydroamination/cyclization at 50 °C. The empirical rate law of −d[substrate]/dt = k′obs[Mg]1[substrate]1 and Michaelis−Menten-type kinetics are consistent with a mechanism involving reversible catalyst−substrate association prior to cyclization. The resting state of the catalyst, ToMMgNHCH2CR2CH2CHCH2 [R = Ph, Me, (CH2)5], is isolable, but isolated magnesium amidoalkene does not undergo unimolecular cyclization at 50 °C. However, addition of trace amounts of substrate allows cyclization to occur. Therefore, we propose a two-substrate, six-center transition state involving concerted CN bond formation and NH bond cleavage as the turnover-limiting step of the catalytic cycle.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja108881s