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Synlett 2004(8): 1355-1358  
DOI: 10.1055/s-2004-825615
LETTER
© Georg Thieme Verlag Stuttgart · New York

Arylboronic Acid-Catalyzed Direct Condensation of Carboxylic Acids with Ureas

Toshikatsu Makia, Kazuaki Ishihara*a, Hisashi Yamamoto*b
a Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
Fax: +81(52)7893222; e-Mail: ishihara@cc.nagoya-u.ac.jp;
b Department of Chemistry, The University of Chicago, 5735 South Ellis Avenue, Chicago, IL 60637, USA
e-Mail: yamamoto@uchicago.edu;
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Publication History

Received 5 March 2004
Publication Date:
18 May 2004 (online)

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Abstract

The first example of the catalytic direct condensation of carboxylic acids with ureas to give N-acylureas, N,N′-diacyl-2-imidazolidones, and poly(N,N′-diacyl-2-imidazolidone)s is described. Arylboronic acids bearing electron-withdrawing substituents are highly effective as catalysts for this condensation. Furthermore, a new and efficient one-pot procedure for the conversion of carboxylic acids and urea to nitriles via N-acylurea intermediates was accomplished by using arylboronic acid and rhenium(VII) oxo complexes as hybrid catalysts.

Key words

acylations - catalysis - condensation - green chemistry - nitriles

21

A commercially available 65-70 wt% aq solution of perrhenic acid was used.

22

Procedure for the Direct Polycondensation of 1,10-Decanedicarboxylic Acid with 2-Imidazolidone . A reaction mixture of 1,10-decanedicarboxylic acid (4 mmol), 2-imidazolidone (4.08 mmol), and 2 (0.4 mmol) in mesitylene (4 mL) was heated at azeotropic reflux with the removal of H2O. After 1 d, the resulting solution was cooled to ambient temperature and concentrated under reduced pressure. The reaction mixture was cooled to precipitate polymeric acylureas and diluted with toluene (ca 20 mL), and the solvents were removed by filtration. The product was dissolved in CHCl3, precipitated into MeOH, and dried at 100 °C under reduced pressure to obtain the desired poly(acylurea) in 95% yield. The DP value, n = 34, was determined by 1H NMR analysis. 1H NMR (300 MHz, CDCl3): δ = 1.18-1.44 (m, 12n H, [O=C(CH2)2 (CH 2)6 (CH2)2C=O) n ], 1.56-1.75 (m, 4n H, [O=CCH2CH 2 (CH2)6CH 2CH2C=O) n ], 2.33 (t, J = 8.4 Hz, 2 H, CH 2CO2H), 2.91 [t, J = 7.8 Hz, 4n H, (O=CCH 2 (CH2)8CH 2C=O) n ], 3.49 (t, J = 8.4 Hz, 2 H, HNCH 2CH2N), 3.83 {s, 4n H, [N(CH 2)2N] n }, 3.95 (t, J = 8.4 Hz, 2 H, HNCH2CH 2N).

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Two linear GPC columns of TSK-gel-SuperHZM-M (4.6 mmID × 15 cm) and TSK-gel-HZ2000 (4.6 mm ID × 15 cm) were employed. The polymer was run at 20 µL (1 mg/mL) in CHCl3 with a polystyrene standard.