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Synlett 2010(14): 2159-2163  
DOI: 10.1055/s-0030-1258510
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Catalyst-Free Process for the Synthesis of 5-Aryl-2-Oxazolidinones via Cycloaddition Reaction of Aziridines and Carbon Dioxide

Xiao-Yong Dou, Liang-Nian He*, Zhen-Zhen Yang, Jing-Lun Wang
State Key Laboratory and Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. of China
Fax: +86(22)23504216; e-Mail: heln@nankai.edu.cn;
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Publication History

Received 2 March 2010
Publication Date:
22 July 2010 (online)

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Abstract

A simple approach for facile synthesis of 5-aryl-2-­oxazolidinones in excellent regioselectivity from aziridines under compressed CO2 conditions was developed in the absence of any catalyst and organic solvent. The reaction outcome was found to be tuned by subtly adjusting CO2 pressure. The adduct formed in situ of aziridine and CO2 is assumed to act as a catalyst in this reaction, which was also studied by means of in situ FT-IR technique.

Key words

carbon dioxide - aziridine - catalyst-free - 5-aryl-2-­oxazolidinones

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Typical Procedure for the Carboxylation of Aziridine with CO 2
In a typical reaction, the carboxylation of aziridine with CO2 was carried out in a 25 mL stainless steel autoclave. Aziridine (1 mmol) was charged into the reactor at r.t. CO2 was introduced into the autoclave, and then the mixture was stirred at predetermined temperature for 20 min to reach the equilibration. The pressure was then adjusted to the desired pressure, and the mixture was stirred continuously. When the reaction finished, the reactor was cooled in ice-water and CO2 was ejected slowly. An aliquot of sample was taken from the resultant mixture and dissolved in dry CH2Cl2 for GC analysis. GC analyses were performed on Shimadzu GC-2014, equipped with a capillary column (RTX-5, 30 m × 0.25 mm × 0.25 µm) using a flame-ionization detector. The residue was purified by column chromatography on silica gel (eluting with 8:1 to 1:1 PE-EtOAc) to furnish the product. The products were further identified by ¹H NMR, ¹³C NMR, and MS which are consistent with those reported in the literature³a-j and in good agreement with the assigned structures.

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Spectral characteristics for representative examples of the products were provided. 3-Ethyl-5-phenyl-2-oxazolidinone (2a)
Colorless liquid. ¹H NMR (300 MHz, CDCl3): δ = 1.17 (t, 3 H, J = 7.2 Hz), 3.29-3.45 (m, 3 H), 3.92 (t, 1 H, J = 8.7 Hz), 5.48 (t, 1 H, J = 7.8 Hz), 7.34-7.42 (m, 5 H). ¹³C NMR (75 MHz, CDCl3): δ = 12.4, 38.8, 51.5, 74.2, 125.4, 128.6, 128.8, 138.8, 157.5. ESI-MS: m/z calcd for C11H13NO2: 191.09; found: 192.29 [M + H]+, 214.38 [M + Na]+, 405.01 [2 M + Na]+.
3-Ethyl-4-phenyl-2-oxazolidinone (3a)
Colorless liquid. ¹H NMR (300 MHz, CDCl3): δ = 1.05 (t, 3 H, J = 5.4 Hz), 2.79-2.88 (m, 1 H), 3.48-3.57 (m, 1 H), 4.10 (t, 1 H, J = 6.0 Hz), 4.62 (t, 1 H, J = 6.6 Hz), 4.81 (t, 1 H, J = 5.4 Hz),7.30-7.44 (m, 5 H). ¹³C NMR (75 MHz, CDCl3): δ = 12.1, 36.9, 59.4, 69.8, 127.0, 129.0, 129.2, 137.9, 158.1. ESI-MS: m/z calcd for C11H13NO2: 191.09; found: 192.29 [M + H]+, 214.38 [M + Na]+.