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Synlett 2006(9): 1367-1368  
DOI: 10.1055/s-2006-939700
LETTER
© Georg Thieme Verlag Stuttgart · New York

Highly Stereoselective Nitration of Chalcone Derivatives with Nitric Oxide

Rui Lia, Zhongquan Liua,b, Yulu Zhoua, Longmin Wu*a
a State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou, Gansu 730000, P. R. of China
b Academy of Organic Chemistry, Gannan Teachers’ College, Ganzhou, Jiangxi 341000, P. R. of China
Fax: +86(931)8625657; e-Mail: nlaoc@lzu.edu.cn;
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Publication History

Received 19 December 2005
Publication Date:
22 May 2006 (online)

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Abstract

A novel nitration of chalcone derivatives with nitric ­oxide affords E-α-nitropropenones exclusively in good yield. The reaction is most likely initiated by electrophilic addition of nitric ­dioxide to the C=C double bond at the α-position.

Key words

stereoselective - nitration - chalcone - nitric oxide - E-2-nitropropenone

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Typical Procedure A stock solution was prepared by dissolving 1a (104 mg, 0.5 mmol) in anhyd CH2Cl2 (100 mL). NO was produced by the reaction of a 1 M H2SO4 solution with a sat. aq solution of NaNO2 under an argon atmosphere (H2SO4 was added dropwise). NO was carried by argon and purified by passing it through a series of scrubbing bottles containing distilled water, 4 M NaOH, and CaCl2 (in this order; bottles were kept under an argon atmosphere). Purified NO was bubbled through the stock solution, which was previously degassed with argon for
6 min. In the course of degassing, the argon flow rate was controlled by regulating the flow-meter at 0.8 Lmin-1 and the stock solution was kept at a pressure of up to +10 mm (water column over local atmospheric pressure at 10 °C). The total amount of NO was passed through the solution estimated to be roughly 300 mmol at local atmospheric pressure using the ideal gas law. After completion of the reaction, as indicated by TLC, the reaction mixture was dried over anhyd MgSO4, concentrated under vacuum, and purified by column chromatography on silica gel (200-300 mesh, EtOAc-PE), giving pure 2a (98 mg, 78%); mp 92 °C. IR (KBr): 3062, 2923, 1679, 1638, 1522, 1316, 1231, 947, 765, 687 cm-1. 1H NMR (300 MHz, CDCl3): δ = 7.35 (m, 2 H), 7.42 (m, 3 H), 7.49 (m, 2 H), 7.63 (m, 1 H), 7.96 (m, 2 H), 8.34 (s, 1 H). 13C NMR (75 MHz, CDCl3): δ = 128.9, 129.2 (2 C), 129.3, 131.0, 132.3, 133.5, 134.9, 137.3, 144.7, 188.2. MS-EI: m/z = 253 (M+), 191, 132, 105, 102, 77, 63. HRMS-ESI: m/z calcd for C15H12NO3: 254.0812; found: 254.0811.