3(2,4-Dinitrobenzyl)-2,4-pentanedione

Molbank 2002, M289

www.molbank.org

3(2,4-Dinitrobenzyl)-2,4-pentanedione

Harald Zieg, Wolfgang Pitsch and Burkhard Koenig*

Institut fuer Organische Chemie, Universitaet Regensburg, D-93040 Regensburg, Germany

Fax (+49) 941 943 171; E-mail: [email protected]

Received: 4 March 2002 / Accepted: 15 March 2002 / Published: 24 February 2003

Keywords: pentanedione, nitro arene

Substituted pentanediones are widely used as ligands for metal complexes.¹ We report the synthesis and characterization of a 3-substituted pentanedione with an electron poor dinitrobenzyl substituent. The compound is sensitive and decomposes readily in the presence of ammonia.

To a solution of sodium acetyl acetonate (1.22 g, 10 mmol) (1) in THF (200 ml) were added 2,4-dinitrobenzylchloride (2.16 g, 10 mmol) (2) in 25 ml of THF at 0 °C. The reaction mixture was heated to reflux 1.5 h and kept at room temperature overnight. The solution was diluted with Et₂O (100 ml), acidified with aqueous HCl (2 M), washed three times with H₂O, dried over MgSO₄ and the solvent was removed in vacuo. The crude product was purified by column chromatography on silica gel [petrol ether (60/70)/Et₂O 3:1] to yield 1.28 g (45 %) of 3 (R_f = 0.35); yellow-orange solid, mp. 118 - 120 °C.

IR (KBr): 3117 cm^-1, 1700, 1604, 1539, 1350, 1174, 734.

UV/Vis (CH₃CN): lmax (log e) = 192 nm (4.248), 200 (4.153), 250 (4.177).

¹H NMR (400 MHz, CDCl₃): Enol form: d = 2.04 (s, 6H, CH₃), 4.08 (s, 2H, benzyl-CH₂), 7.54 (d, 3J = 8.7 Hz, 1H, arene-H), 8.42 (dd, 3J = 8.7 Hz, 4J = 2.4 Hz, 1H, arene-H), 8.84 (m, 1H, arene-H), 16.96 (s, 1H, enol-H). Keto form: d = 2.27 (s, 6H, CH₃), 3.49 (d, 3J = 6.7 Hz, 2H, benzyl-CH₂), 4.20 (t, 3J = 6.7 Hz, 1H, CH), 7.74 (d, 3J = 8.5 Hz, 1H, arene-H), 8.36 (dd, 3J = 8.5 Hz, 4J = 2.4 Hz, 1H, arene-H), 8.84 (m, 1H, arene-H).

¹³C NMR (100 MHz, CDCl₃): d = 23.16 (+), 30.04 (+), 30.17 (-), 30.89 (-), 67.14 (+), 105.00 (C_quat), 120.51 (+), 120.57 (+), 127.22 (+), 127.40 (+), 130.30 (+), 135.32 (+), 140.60 (C_quat), 141.66 (C_quat), 192.31 (C_quat), 201.84 (C_quat).

MS (70 eV), m/z (%): 237 (2) [M+-CO-CH₃], 43 (100) [CO-CH₃].

EA Calculated (%): C 51.43 H 4.32 N 10.00
found (%): C 51.26 H 4.31 N 9.96.

References and Notes

1. Murakami, Y.; Nakamura, K.; Uchida, H.; Kanaoka, Y. Inorg. Chim. Acta, 1968, 2(2), 133 - 8.

Sample availability: available form the authors.