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

TitleConcerted C-N and C-H Bond Formation in a Magnesium-Catalyzed Hydroamination
Publication TypeJournal Article
Year of Publication2010
AuthorsDunne JF, Fulton DB, Ellern A, Sadow AD
Journal TitleJournal of the American Chemical Society
Volume132
Pages17680-17683
Date Published12/22
ISBN Number0002-7863
Accession NumberISI:000285429800013
Keywordsalkenes, alkyl derivatives, amido bond, aminoalkene, complexes, insertion, internal alkynes, intramolecular hydroamination, mechanism, unprotected amino olefins
Abstract

Coordinatively saturated To(M)MgMe (1; To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) is an active precatalyst for intramolecular hydroamination/cyclization at 50 degrees 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, To(M)MgNHCH(2)CR(2)CH(2)CH=CH2 [R = Ph, Me, -(CH2)(5)-], is isolable, but isolated magnesium amidoalkene does not undergo unimolecular cyclization at 50 degrees 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.

URL<Go to ISI>://000285429800013
DOI10.1021/Ja108881s
Alternate JournalJ Am Chem Soc