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S. Koguchi et al.
Letter
Synlett
With this system, the halogenation of alcohols proceeded
well (Table 2, entries 1–5). However, when the slightly larg-
er alcohol (4-phenoxyphenyl)methanol was used, the yield
decreased slightly (entry 6).
Supporting Information
Supporting information for this article is available online at
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Finally, we examined the reuse of this reaction system.
Ether was added to the ionic-liquid phase after completion
of the reaction to extract the target compound. Then, oxalyl
chloride was added to the ionic-liquid phase to convert the
ionic-liquid-supported DMI ([DMI] PF6; 7) back into ionic-
liquid-supported DMC ([DMC]PF6) in situ. Fresh reagents
were then added to the ionic-liquid phase, and the reaction
was run again. As mentioned before, the synthesis of this
novel ionic-liquid catalyst, the ionic-liquid separation, and
the recycling of the product are operationally simple. Excel-
lent conversions were obtained for up to five consecutive
cycles of recycling and reuse (Table 3).
References and Notes
(1) (a) Fujii, S. Yuki Gosei Kagaku Kyokaishi 1994, 52, 778. (b) Zhao,
L.-M.; Zhang, S.-Q.; Jin, H.-S/.; Wan, L.-J.; Dou, F. Org. Lett. 2012,
14, 886. (c) Kitamura, T.; Gondo, K.; Katagiri, T. J. Org. Chem.
2013, 78, 3421.
(2) Akiyama, A.; Hanamura, H.; Imatomi, S.; Yamada, S.; Itou, H.;
Kondou, H.; Maeshima, Y. JP 2018024818, 2018.
(3) (a) Isobe, T.; Ishikawa, T. J. Org. Chem. 1999, 64, 6984. (b) Isobe,
T.; Ishikawa, T. J. Org. Chem. 1999, 64, 6989. (c) Isobe, T.;
Ishikawa, T. J. Org. Chem. 1999, 64, 5832.
(4) Disadee, W.; Watanabe, T.; Ishikawa, T. Synlett 2003, 115.
(5) (a) Hallett, J. P.; Welton, T. Chem. Rev. 2011, 111, 3508.
(b) Wasserscheid, P.; Welton, T. Ionic Liquids in Synthesis; Wiley-
VCH: Weinheim, Germany, 2007. (c) Wasserscheid, P.; Keim, W.
Angew. Chem. Int. Ed. 2000, 39, 3772. (d) Welton, T. Chem. Rev.
1999, 99, 2071.
Table 3 Recovery and Reuse of the Ionic-Liquid Phase Containing the
Ionic-Liquid-Supported DMIa
reuse
(6) (a) Marra, A.; Chiappe, C.; Mele, A. Chimia 2011, 65, 76. (b) Xue,
H.; Shreeve, J. M. Eur. J. Inorg. Chem. 2005, 2573.
Ionic-liquid-supported DMI
[DMI]PF6 (7)
(7) Cao, H.; McNamee, L.; Alper, H. J. Org. Chem. 2008, 73, 3530.
(8) (a) Koguchi, S. Trans. Mater. Res. Soc. Jpn. 2013, 38, 35.
(b) Matsumoto, H.; Yanagida, M.; Tanimoto, K.; Nomura, M.;
Kitagawa, Y.; Miyazaki, Y. Chem. Lett. 2000, 29, 922. (c) Sakaebe,
H.; Matsumoto, H. Electrochem. Commun. 2003, 5, 594.
(9) (a) Koguchi, S.; Izawa, K. ACS Comb. Sci. 2014, 16, 381.
(b) Koguchi, S.; Mihoya, A.; Mimura, M. Tetrahedron 2016, 72,
7633. (c) Koguchi, S.; Nakamura, K. Synlett 2013, 24, 2305.
(10) Chlorination of Alcohols (Table 2); General Procedure
The solution of ionic-liquid-supported DMI 7 (2.2 mmol) in
[bmim]PF6 (2 mL) was added to oxalyl chloride (2.0 mmol), and
the mixture was stirred at 60 °C for 2 h. The mixture was then
added to the appropriate alcohol (1.5 mmol), and the resulting
mixture was stirred at r.t. overnight. Finally, the mixture was
extracted with hexane 10 mL x 3, and the organic layer was
concentrated.
[bmim]PF6
OH
Cl
O
O
oxalyl chloride
r.t., 24 h
Run
Yieldb (%)
1
2
3
4
5
93
92
95
97
93
a Reagents and conditions: 4-methoxybenzyl alcohol (1.5 mmol), 7 (2.2
mmol), oxalyl chloride (2.0 mmol), [bmim]PF6 (2 mL), r.t., 24 h.
b Yield of the isolated product.
In summary, we synthesized hydrophobic ionic-liquid-
supported DMI and demonstrated that it can be used in the
halogenation of alcohols.10 A base is not required in this re-
action. After completion of the reaction, purification steps,
such as column chromatography, are not required because
the product can be extracted. After the reaction, the ionic-
liquid reagent can be regenerated by using oxalyl chloride.
This system is advantageous because of its environmental
friendliness and good yields. Moreover, this reaction system
can be reused up to five times.
1-(2-hydroxyethyl)imidazolidin-2-one (2)
The solution of 2-((2-aminoethyl) amino) ethanol (6.24g,
60mmol) in ethylene glycol (4 ml) was added to ureal (3.60g, 60
ml). The mixture was stirred at 130 °C for 24 h. The mixture
extracted with ethyl acetate, and organic layer was washed with
H2O, dried (MgSO4) and evaporated. The product was isolated by
silica gel column chromatography to give the title compound 2
(6.94 g, 89%) as white solid; mp 45 °C. 1H NMR (500 MHz,
CDCl3): =3.30–3.77 (9H, m), 5.80 (1H, s). 13C NMR (CDCl3) =
38.4, 46.0, 46.3, 60.2, 164.0. HRMS (APCI): m/z [M + H]+ calcd for
C5H11N2O2, 131.08205; found: 131.08390.
Funding Information
1-(2-chloroethyl)imidazolidin-2-one (3)
The solution of 1-(2-hydroxyethyl) imidazolidin-2-one (5.07g,
39.1mmol) in chloroform (10 ml) was added to thionyl chloride
(5.70ml, 78.2mmol). The mixture was stirred at 50 °C for 3 h.
The mixture was evaporated, and the product was isolated by
silica gel column chromatography to give the title compound 3
(5.50 g, 95%) as white solid; mp 85–88 °C. 1H NMR (500 MHz,
CDCl3): = 3.45–3.64 (8H, m), 5.60 (1H, s). 13C NMR (CDCl3) =
38.3, 42.5, 45.6, 46.0, 163.0. HRMS (APCI): m/z [M + Na]+ calcd
for C5H9ClN2NaO, 171.03011; found: 170.03091.
This work was supported by Tokai University General Research Orga-
nization Grant.()
Acknowledgment
I would particularly like to thank Dr. Yoshiki Oda for his valuable sup-
port on this work.
© Georg Thieme Verlag Stuttgart · New York — Synlett 2019, 30, A–D