ACS Catalysis
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Benzoxazoles from Primary Amines by ortho-Quinone Catalysis.
Org. Lett. 2017, 19, 5629-5632.
16. Upon using other nitroalkanes, no side reaction was observed.
However, the reaction conversion was low (3c, 35% yield using
CH3NO2 and 47% yield using CH3CH2NO2 after 12 h).
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8. For selected examples, see: (a) Li, B.; Wendlandt, A. E.; Stahl,
S. S. Replacement of Stoichiometric DDQ with a Low Potential o-
Quinone Catalyst Enabling Aerobic Dehydrogenation of Tertiary
Indolines in Pharmaceutical Intermediates. Org. Lett. 2019, 21, 1176-
1181. (b) Zhang, R.; Qin, Y.; Zhang, L.; Luo, S. Mechanistic Studies
on Bioinspired Aerobic C-H Oxidation of Amines with an ortho-
Quinone Catalyst. J. Org. Chem. 2019, 84, 2542-2555.
9. For selected examples, see: (a) Qin, Y.; Zhang, L.; Lv, J.; Luo,
S.; Cheng, J.-P. Bioinspired Organocatalytic Aerobic C-H Oxidation
of Amines with an ortho-Quinone Catalyst. Org. Lett. 2015, 17, 1469-
1472. (b) Largeron, M.; Fleury, M.-B. A Bioinspired Organocatalytic
Cascade for the Selective Oxidation of Amines under Air. Chem. -
Eur. J. 2017, 23, 6763-6767.
10. (a) Kim, H. Y.; Takizawa, S.; Oh, K. Copper-catalyzed
Divergent Oxidative Pathways of 2-Naphthol Derivatives: ortho-
Naphthoquinone versus 2-BINOLs. Org. Biomol. Chem. 2016, 14,
7191-7196. (b) Golime, G.; Kim, H. Y.; Oh, K. Rhodium(I)-
Catalyzed Decarbonylative Aerobic Oxidation of Cyclic a-Diketones:
A Regioselective Single Carbon Extrusion Strategy. Org. Lett. 2018,
20, 942-945.
11. (a) Goriya, Y.; Kim, H. Y.; Oh, K. o-Naphthoquinone-
Catalyzed Aerobic Oxidation of Amines to (Ket)imines: A Modular
Catalyst Approach. Org. Lett. 2016, 18, 5174-5177. (b) Kim, K.; Kim,
H. Y.; Oh, K. Aerobic Oxidation Approaches to Indole-3-
carboxylates: A Tandem Cross Coupling of Amine-Intramolecular
17. The N-nitrosation of aromatic primary amines, for example
benzylamines (including -branched benzylamines), provided the
corresponding N-nitro amines in low yields (>10%) due to the
inherent thermal instability of products. For the diazotization of
primary amines via N-nitroso compounds, see: Moumne, R.; Lavielle,
S.; Karoyan, P. Efficient Synthesis of 2-Amino Acid by
Homologation of -Amino Acids Involving the Reformatsky
Reaction and Mannich-Type Imminium Electrophile. J. Org. Chem.
2006, 71, 3332-3334.
18. The formation of (1,3-dinitropropan-2-yl)benzene, a tandem
Michael addition of CH3NO2 to nitroalkene product 5a, could be
improved to 60% under slightly modified conditions. This reaction
will be reported elsewhere.
19. The second-order rate constants were influenced by the steric
bulkiness of alkyl groups of nitronates, see: Bu, T.; Lemek, T.; Mayr,
H. Nucleophilicities of Nitroalkyl Anions. J. Org. Chem. 2004, 69,
7565-7576.
20. Currently, the quinone-catalyzed amine oxidation protocols are
not applicable to alkyl amines, possibly due to the imine-enamine
isomerization of catalyst-amine adducts.
21. For a review, see: Ballini, R.; Petrini, M. The Nitro to Carbonyl
Conversion (Nef Reaction): New Perspectives for a Classical
Transformation. Adv. Synth. Catal. 2015, 357, 2371-2402.
22. For a review, see: Wang, P. G.; Xian, M.; Tang, X.; Wu, X.;
Wen, Z.; Cai, T.; Janczuk, A. J. Nitric Oxide Donors: Chemical
Activities and Biological Applications. Chem. Rev. 2002, 102, 1091-
1134.
23. While the use of nitrocyclopentane provided the desired N-
nitroso compound 3a in 20% yields after 12 h at 100 C, the
formation of Nef-type reaction product, cyclopentanone from
nitrocyclopentane, could be monitored by the NMR spectra of the
crude reaction mixture (see the Supporting Information for detail).
24. The loss of HNO is the rate limiting step above pH 3.8 and is
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Mannich-Oxidation
Sequence.
Org.
Lett.
2019,
21,
doi.org/10.1021/acs.orglett.9b02348.
12. Golime, G.; Bogonda, G.; Kim, H. Y.; Oh, K. Biomimetic
Oxidative Deamination Catalysis via ortho-Naphthoquinone-
Catalyzed Aerobic Oxidation Strategy. ACS Catal. 2018, 8, 4986-
4990.
13. For the use of stoichiometric oxidants, see: (a) Challis, B. C.;
Yousaf, T. I. Facile Formation of N-Nitrosamines from
Bromonitromethane and Secondary Amines. J. Chem. Soc., Chem.
Commun. 1990. 1598-1599. (b) Zhang, J.; Jiang, J.; Li, Y.; Wan, X.
Iodide-Catalyzed Synthesis of N-Nitrosoamines via CN Cleavage of
Nitromethane. J. Org. Chem. 2013, 78, 11366-11372. (c) Yu, F.-C.;
Hao, X.-P.; Huang, R.; Yan, S.-J.; Lin, J. Synthesis of 2-Nitroso
Heterocyclic Ketene Aminals with (E)-1-Nitro-4-(2-nitrovinyl)-
benzene as the Nitrosating Agent. Tetrahedron 2015, 71, 2306-2312.
(d) Chaudhary, P.; Gupta, S.; Muniyappan, N. Sabiah, S.;
Kandasamy, J. An Efficient Synthesis of N-Nitrosamines under
Solvent, Metal and Acid Free Conditions Using tert-Butyl Nitrite.
Green Chem. 2016, 18, 2323-2330. (e) Azeez, S.; Chaundhary, P.;
Sureshbabu, P.; Sabiah, S.; Kandasamy, J. Potassium Persulfate-
Promoted N-Nitrosation of Secondary and Tertiary Amines with
Nitromethane under Mild Conditions. Asian J. Org. Chem. 2018, 7,
2113-2119. (f) Qiu, S.; Guo, C.; Wang, M.; Sun, Z.; Li, H.; Qian, X.;
Yang, Y. Mild Dealkylative N-Nitrosation of N,N-Dialkylaniline
Derivatives for Convenient Preparation of Photo-Triggered and
Photo-Calibrated NO Donors. Org. Chem. Front. 2018, 5, 3206-3209.
(g) Chaudhary, P.; Gupta, S.; Muniyappan, N.; Sabiah, S.;
Kandasamy, J. Regioselective Nitration of N-Alkyl Anilines Using
tert-Butyl Nitrite under Mild Condition. J. Org. Chem. 2019, 84, 104-
119. For a catalytic method, see: (h) Sakai, N.; Sasaki, M.; Ogiwara,
Y. Copper(II)-Catalyzed Oxidative N-Nitrosation of Secondary and
Tertiary Amines with Nitromethane under an Oxygen Atmosphere.
Chem. Commun. 2015, 51, 11638-11641.
preceded by
a rapid equilibrium nitrosation-denitrosation, see:
Gowenlock, B. G.; Hutchison, R. J.; Little, J.; Pfab, J. Nitrosative
Dealkylation of Some Symmetric Tertiary Amines. J. Chem. Soc.
Perkin Trans.2, 1979, 1110-1114.
25. The use of wet nitropropane did not facilitate the N-nitrosation
of tertiary amines, supporting the intramolecular HNO elimination,
see: (a) Smith, P. A. S.; Loeppky, R. N.; Nitrosative Cleavage of
Tertiary Amines. J. Am. Chem. Soc. 1967, 89, 1147-1157. (b)
Leoppky, R. N.; Tomasik, W. Stereoelectronic Effects in Tertiary
Amine Nitrosation: Nitrosative Cleavage vs. Aryl Ring Nitration. J.
Org. Chem. 1983, 48, 2751-2757.
26. The use of 1 equiv of TEMPO under the optimized N-
nitrosation conditions resulted in the formation of 3a in 85% yield
(89% in the absence of TEMPO).
27. (a) Filarowski, A. Intramolecular Hydrogen Bonding in o-
Hydroxyaryl Schiff Bases. J. Phys. Org. Chem. 2005, 18, 686-698.
(b) Makal, A.; Schilf, W.; Kamienski, B.; Szady-Chelmieniecka, A.;
Grech, E.; Wozniak, K. Hydrogen Bonding in Schiff Bases NMR,
Structural and Experimental Charge Density Studies. Dalton Trans.
2011, 40, 421-430.
28. The formation of homo-imine adducts has been observed from
1
the crude reaction mixtures with low conversion by H NMR in <5%
yields.
29.
A control experiment using benzaldehyde instead of
14. The 2HCl salts were freed by treating them with aq. K2CO3,
and extracted with using ethyl acetate. After removing the solvent, the
prolinates were used directly. The low chemical yields for N-
nitrosation might be due to the decomposition/loss of prolinates upon
the experimental handling of prolinates under basic conditions.
15. The formation of 3,4-dihydroisoquinoline, an imine derived
from 3x, was observed in 30% yield under the optimized N-
nitrosation conditions.
benzylamine under the optimized reaction conditions did not provide
the nitroalkene product at all, suggesting the critical role of o-NQ2 in
the deaminative cross-coupling reaction.
30. For a review, see: Huang, J.; Chen, Z.; Yuan, J.; Peng, Recent
Advances in Highly Selective Applications of Nitroso Compounds.
Asian, J. Org. Chem. 2016, 5, 951-960.
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