Organic Letters
Letter
was also observed. The asymmetric transformations are going
to be investigated in our laboratory.
Table 2. Carbocation Trapping Experiments
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
Experimental details, characterization data, and NMR
spectra of new compounds (PDF)
entry
solvent
additive
2a (%)
4a (%)
Accession Codes
1
2
3
4
MeCN
MeCN
DME
/
15
25
16
14
8
29
41
CCDC 1814175 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge
bridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
NiCl2
/
Zn(OTf)2
DME
trace
On the basis of the results above and previously reported
literature,5a,14 plausible mechanisms are proposed (Scheme 6).
AUTHOR INFORMATION
Scheme 6. Proposed Mechanism
■
Corresponding Author
ORCID
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
We gratefully acknowledge the financial support from NSFC
(21472162, 21772171), the National Basic Research Program
of China (2015CB856600), the Zhejiang Provincial Natural
Science Foundation of China (LR19B020001) and Zhejiang
University.
REFERENCES
■
The photocatalyst (PC) absorbs the visible light to generate
the excited state PC* which can be reduced by the electron
sacrifice to produce the reduced photocatalyst PC− and
trialkylammonium radical cation. The substrate 1a can be
reduced by PC− species to regenerate PC and afford the radical
ion intermediate which may undergo N−O bond cleavage to
form an amidyl radical C. The primary amidyl radical can
undergo the intramolecular 1,5-HAT to afford an alkyl radical
D, which is easily oxidized to alkyl carbocation B by PC*.14
Oxidation via trialkylammonium radical cation cannot be ruled
out. The nickel(II) complex might coordinate with the slightly
“harder” oxygen atom on carbamate which led the nitrogen
atom to attack the alkyl carbocation to give 2a. On the other
hand, Zn2+ might coordinate with slightly “softer” nitrogen
atom on carbamate which led the oxygen atom to attack the
alkyl carbocation to give 3a. Experimental and computational
studies will be further conducted to gain an accurate
understanding of the mechanisms.
In summary, we developed dual catalyst-controlled intra-
molecular unactivated C(sp3)-H amination and oxygenation of
carbamates. Amino alcohol and diol derivatives could be easily
obtained from readily available alcohol derivatives by merging
visible light photocatalyst with nickel and zinc catalysts,
respectively. The alternative possible mechanisms were
proposed via 1,5-HAT process followed by catalyst-controlled
cyclization. An interesting phenomenon of chirality transfer
(1) For selected reviews on the use of vicinal amino alcohols and
diols, see: (a) Ager, D. J.; Prakash, I.; Schaad, D. R. Chem. Rev. 1996,
96, 835−875. (b) Donohoe, T. J.; Callens, C. K. A.; Flores, A.; Lacy,
A. R.; Rathi, A. H. Chem. - Eur. J. 2011, 17, 58−76. (c) Song, Z.-L.;
Fan, C.-A.; Tu, Y.-Q. Chem. Rev. 2011, 111, 7523−7556.
(2) For selected reviews on the synthesis of vicinal amino alcohols
and diols, see: (a) Lohray, B. B.; Ahuja, J. R. J. Chem. Soc., Chem.
Commun. 1991, 95−97. (b) Kolb, H. C.; VanNieuwenhze, M. S.;
Sharpless, K. B. Chem. Rev. 1994, 94, 2483−2547. (c) Larrow, J. F.;
Schaus, S. E.; Jacobsen, E. N. J. Am. Chem. Soc. 1996, 118, 7420−
7421. (d) Mun
A.; Muniz, K. Chem. Soc. Rev. 2007, 36, 1142−1152. (f) McDonald, R.
̃
iz, K. Chem. Soc. Rev. 2004, 33, 166−174. (e) Minatti,
̃
I.; Liu, G.; Stahl, S. S. Chem. Rev. 2011, 111, 2981−3019. (g) Cao,
M.; Ren, X.; Lu, Z. Tetrahedron Lett. 2015, 56, 3732−3742.
(3) (a) Giri, R.; Shi, B.-F.; Engle, K. M.; Maugel, N.; Yu, J.-Q. Chem.
Soc. Rev. 2009, 38, 3242−3272. (b) Lyons, T. W.; Sanford, M. S.
Chem. Rev. 2010, 110, 1147−1169. (c) Newhouse, T.; Baran, P. S.
Angew. Chem., Int. Ed. 2011, 50, 3362−3374. (d) White, M. C. Science
2012, 335, 807−809. (e) Ramirez, T. A.; Zhao, B.; Shi, Y. Chem. Soc.
Rev. 2012, 41, 931−942. (f) Thirunavukkarasu, V. S.; Kozhushkov, S.
I.; Ackermann, L. Chem. Commun. 2014, 50, 29−39.
(4) Strambeanu, I. I.; White, M. C. J. Am. Chem. Soc. 2013, 135,
12032−12037.
(5) (a) Ren, X.; Guo, Q.; Chen, J.; Xie, H.; Xu, Q.; Lu, Z. Chem. -
Eur. J. 2016, 22, 18695−18699. (b) Yang, B.; Lu, Z. Chem. Commun.
2017, 53, 12634−12637. (c) Yang, B.; Lu, Z. ACS Catal. 2017, 7,
8362−8365. (d) Yang, B.; Ren, X.; Shen, X.; Li, T.; Lu, Z. Chin. J.
Chem. 2018, 36, 1017−1023.
D
Org. Lett. XXXX, XXX, XXX−XXX