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Green Chemistry
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ARTICLE
Journal Name
completion of reaction (TLC), cooled, and concentrated under
reduced pressure. The residue was partitioned between MTBE
and 1 M HCl, the organic phase was separated and washed
successively with water and brine, dried over Na2SO4, and
purified by flash column chromatography (EA/PE = 1/30).
18, 15578.
DOI: 10.1039/C9GC01650C
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8
S. Hase, Y. Kayaki and T. Ikariya, ACS Catal. 2015, 5, 5135.
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9
P. Brunel, J. Monot, C. E.Kefalidis, L. Maron, B. Martin-Vaca
and D. Bourissou, ACS Catal. 2017, 7, 2652.
1
Compound 3b: 59% yield, H NMR (400 MHz, CDCl3) δ 7.69–
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7.54 (m, 3H), 7.47 – 7.37 (m, 3H), 6.90 (d, J = 16.1 Hz, 1H), 2.34
– 2.21 (m, 1H), 1.18 (dt, J = 6.8, 3.4 Hz, 2H), 1.00 (dt, J = 7.3,
3.7 Hz, 2H).
12 (a) R. Robles-Machin, J. Adrio and J. C. Carretero, J. Org.
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13 P. Garcia-Dominguez, L. Fehr, G. Rusconi and C. Nevado,
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14 For a leading overview of organic reactions in water, see: C.-
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Aqueous Media, 2nd Ed., Wiley-Interscience, 2007.
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16 For an example of gas–free process using ammonium
carbamate as a CO2 surrogate, see: Q.-W. Song, Z.-H. Zhou, H.
Yin and L.-N. He, ChemSusChem, 2015, 8, 3967.
Conclusions
In summary, we have developed an environment-friendly
synthesis of Z-5-alkylidene-2-oxazolidinones, which is carried
out in neat water under gas-free conditions. This protocol is
amenable to primary propargylic amines with a wide variety of
substitution patterns. It is notable that potassium bicarbonate
is used as a low cost CO2 surrogate. We have also investigated
the associated C−N cleavage side reaction for substrates with
an alkyl -substituent and identified an interesting solvent
effect. In neat water this side reaction is negligible, while in 95%
aqueous ethanol it becomes the major pathway.
Mechanistically, it involved a 6-endo-dig cyclisation and
subsequent base-induced ring-opening and elimination of
urethane.
17 S. D. Burley, V. V. Lam, F. J. Lakner, B. M. Bergdahl and M. A.
Parker, Org. Lett. 2013, 15, 2598.
18 A. P. Ronaldo, M. V. Mauricio and M. Armin, J. Org. Chem.
2000, 65, 5910.
19 R. Yuan and Z. Lin, ACS Catal. 2015, 5, 2866.
20 AgHCO3 [10357-62-7] was reported in a recent patent
application to be unstable to moisture, and was thus used as
a water scavenger: R.-J. Zhou, S.-H. Chen, B. Li and H.-X. Liu,
CN108774208 (2018).
Conflicts of interest
There are no conflicts to declare.
21 For the role of bicarbonate in related amine carboxylation,
see: (a) Y.-S. Choi, H. Kim, S. H. Shin, M. Cheong, Y. J. Kim, H.
G. Jang, H. S. Kim and J. S. Lee, Appl. Catal. B: Environmental,
2014, 144, 317. (b) S.-J. Jin, Y. Khan, J. H. Maeng, Y. J. Kim, J.
Hwang, M. Cheong, J. S. Lee and H. S. Kim, Appl. Catal. B:
Environmental, 2017, 209, 139.
Acknowledgements
Financial support from the National Natural Science
Foundation (No. 21272039) is gratefully acknowledged.
22 C−N cleavage of propargylic amine has only been reported in
the context of removing simple N-propargyl as a protective
group, no study has been reported on the transformation of
more sophisticated propargylic moiety. For selected
examples of cleavage of other types of C−N bond, see: (a)
M. B. Li, Y. Wang and S. K. Tian, Angew. Chem., Int. Ed. 2012,
51, 2968. (b) H. Huang, X. Ji, W. Wu, L. Huang and H. Jiang, J.
Org. Chem. 2013, 78, 3774. (c) X. Zhao, D. Liu, H. Guo, Y. Liu
and W. Zhang, J. Am. Chem. Soc. 2011, 133, 19354. For a
review, see: (d) K. Ouyang, W. Hao, W.-X. Zhang and Z. Xi,
Chem. Rev. 2015, 115, 12045.
Notes and references
‡ Unreacted amine was easily separated and recovered during
workup by simple acid-base workup.
§ Compounds 3 may be volatile.
1
2
(a) D. A. Evans, J. Bartroli and T. L. Shih, J. Am. Chem. Soc.
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23 T. Ishida, R. Kobayashi and T. Yamada, Org. Lett. 2014, 16,
2430.
24 We obtained tetramic acid 4a in a high yield from 2a under
aqueous basic conditions (Scheme 2).
3
4
T. Mitsudo, Y. Hori, Y. Yamakawa and Y. Watanabe,
Tetrahedron Lett. 1987, 28, 4417.
W.-J. Yoo and C.-J. Li, Adv. Synth. Catal. 2008, 350, 1503. For
a very similar example, see: B. Yu, B.-B. Cheng, W.-Q. Liu, W.
Li, S.-S. Wang, J. Cao and C.-W. Hu, Adv. Synth. Catal. 2016,
358, 90.
O
O
O
O
C
N
LiOH
aq. THF
Ph
HO-
H
N
O
HN
Ph
HN
Ph
Ph
Ph
OH
Ph
Ph
5
For reviews of A3-coupling, see: a) W.-J. Yoo, L. Zhao and C.-J.
Li, Aldrichimica Acta 2011, 44, 43. b) C. Wei, Z. Li and C.-J. Li
Synlett 2004, 1472. c) V. A. Peshkov, O. P. Pereshivko and E.
V. Van der Eycken, Chem. Soc. Rev. 2012, 41, 3790.
(a) S. Yoshida, K. Fukui, S. Kikuchi and T. Yamada, Chem. Lett.
2009, 38, 786. For a Ag/DBU dual catalyst protocol, see: (b)
Ph
O
O
2a
4a, 95% yield
Scheme 2. Formation of tetramic acid 4a in attempted
hydrolysis of oxazolidinone.
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6 | J. Name., 2012, 00, 1-3
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