Organic Letters
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stable organic peroxides and requires elevated temperatures for
uncatalyzed decomposition.
parameters.
(14) For industrial synthesis of benzophenone imine from
benzophenone, see: Method of Producing Benzophenone Imines.
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(15) Lowest listed price on SciFinder: $67 (USD)/2.5L from
Beantown Chemical Corporation.
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(17) In terms of practicality, the method by White et al. is sensitive
to light and air, while our method can be performed in air without the
exclusion of light. Ph2CNH is commercially available ($188/25g),
while White’s nitrogen reagent (2.0 equiv used) has to be synthesized
from 2,2,2-trichloroethyl sulfamate ($306/10g) and PhI(OAc)2
($144/100g) providing a 47% yield (prices are from www.
starting from scratch, our method requires two steps (one-pot) to the
unprotected amine, while the method reported by White et al.
requires five steps (includes catalyst synthesis, nitrogen reagent
synthesis, and deprotection).
(7) For reviews on CDC, see: (a) Li, C.-J. Cross-Dehydrogenative
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(18) In the absence of CuI/phen, 1% of 3 was formed.
(19) Ryan, M. C.; Martinelli, J. R.; Stahl, S. S. Cu-Catalyzed Aerobic
Oxidative N−N Coupling of Carbazoles and Diarylamines Including
Selective Cross-Coupling. J. Am. Chem. Soc. 2018, 140, 9074−9077.
(20) In the absence of CuI/phen, 0.5% of 4 was observed.
(8) For recent examples of copper-catalyzed cross-coupling involving
benzylic C−H functionalization, see: (a) Zhang, W.; Wang, F.;
McCann, S. D.; Wang, D.; Chen, P.; Stahl, S. S.; Liu, G.
Enantioselective Cyanation of Benzylic C−H Bonds via Copper-
Catalyzed Radical Relay. Science 2016, 353, 1014−1018. (b) Vasilo-
poulos, A.; Zultanski, S. L.; Stahl, S. S. Feedstocks to Pharmaco-
phores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes
Enabling Direct Access to Diarylalkanes. J. Am. Chem. Soc. 2017, 139,
7705−7708. (c) Zhang, W.; Chen, P.; Liu, G. Copper-Catalyzed
Arylation of Benzylic C−H Bonds with Alkylarenes as the Limiting
Reagents. J. Am. Chem. Soc. 2017, 139, 7709−7712.
(9) For synthesis of nonprimary benzylamines by copper-catalyzed
benzylic C−N formation, see: (a) Pelletier, G.; Powell, D. A. Copper-
Catalyzed Amidation of Allylic and Benzylic C−H Bonds. Org. Lett.
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Mossin, S.; Varonka, M. S.; Melzer, M. M.; Meyer, K.; Cundari, T. R.;
Warren, T. H. Catalytic C−H Amination with Unactivated Amines
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8855. (c) Gephart, R. T.; Huang, D. L.; Aguila, M. J. B.; Schmidt, G.;
Shahu, A.; Warren, T. H. Catalytic C−H Amination with Aromatic
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̈
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(10) For copper-catalyzed aliphatic C−N bond formation by C−H
functionalization, see: Tran, V.; Li, V.; Driess, M.; Hartwig, J. F.
Copper-Catalyzed Intermolecular Amidation and Imidation of
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(11) To avoid potential catalysis by trace metal impurities, 99.999%
CuI was used.
(12) Chorobenzene is considered as “green” as acetonitrile, toluene,
heptane, and methyl-THF, and greener than commonly used solvents
such as THF, 1,4-dioxane, cyclohexane, DMA, MTBE, and benzene:
Byrne, F. P.; Jin, S.; Paggiola, G.; Petchey, T. H. M.; Clark, J. H.;
Farmer, T. J.; Hunt, A. J.; McElroy, C. R.; Sherwood, J. Tools and
Techniques for Solvent Selection: Green Solvent Selection Guides.
Sustainable Chem. Processes 2016, 4, 7. (t-BuO)2 is one of the most
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