Synlett 2008(19): 3053-3057  
DOI: 10.1055/s-0028-1083627
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Zinc(II) Iodide-Triethylsilane: A Novel Mild Reduction System for Direct Deoxygenation of Aryl Aldehydes, Ketones, and α,β-Unsaturated Enones

Zheng Li, Gang Deng, Yuan-Chao Li*
Department of Medicinal Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Zhangjiang Hi-Tech Park, Pudong, Shanghai 201203, P. R. of China
Fax: +86(21)50807288; e-Mail: ycli@mail.shcnc.ac.cn;
Weitere Informationen

Publikationsverlauf

Received 7 July 2008
Publikationsdatum:
12. November 2008 (online)

Abstract

ZnI2-TESH has been found to be a novel mild and efficient reduction system. This reagent, in contrast to the traditional ionic deoxygenation systems (TFA-R3SiH, BF3˙OEt2-R3SiH, etc.), could directly deoxygenate different kinds of carbonyl compounds such as aryl aldehydes, ketones, and α,β-unsaturated enones to the corresponding hydrocarbons in moderate to excellent yields.

14

Deng, G.; Zhao, X. L.; Li, Z.; Jiang, B.; Li, Y. C. unpublished results.

19

General Procedure for the Synthesis of Product 2: To a stirred solution of substrate 1 (1 mmol) in 1,2-dichloroethane (5 mL) at r.t. was added solid zinc iodide (638 mg, 2 mmol).Then, triethylsilane (1.9 mL, 10 mmol) was added slowly to the above suspension via a syringe. The reaction mixture was stirred at r.t. until 1 was completely disappeared or there was no further conversion (TLC inspection). The stirring was stopped, and then the reaction mixture was filtered through Celite. The Celite was washed with CH2Cl2 (4 × 15 mL). The combined filtrate was washed with H2O and sat. brine, and then dried over anhyd Na2SO4. After concentration, the residue was chromatographed on silica gel, eluting with 0-25% EtOAc in cyclohexane.

20

Analytic Data for 4-Chloro-2-[2,2,2-trifluoro-1-(triethyl-silyloxy)ethyl]aniline (2j): ¹H NMR (300 MHz, CDCl3): δ = 0.62 (q, J = 7.9 Hz, 6 H), 0.92 (t, J = 7.9 Hz, 9 H), 3.93 (br s, 2 H), 4.94 (q, J = 7.2 Hz, 1 H), 6.60 (d, J = 8.5 Hz,
1 H), 7.09 (dd, J = 8.5, 2.5 Hz, 1 H), 7.15 (d, J = 2.5 Hz, 1 H). MS (EI): m/z (%) = 339 (39) [M+], 322 (4), 310 (43), 190 (32), 188 (100), 77 (36). HRMS (EI): m/z calcd for C14H21NOSiClF3: 339.1033; found: 339.1041.

23

Analytic Data for 5-[(4-Hydroxy-3-methoxyphenyl)-methyl]-2-methoxy-4-methylphenol (2d-2): ¹H NMR (300 MHz, CDCl3): δ = 2.19 (s, 3 H), 3.80 (s, 2 H), 3.82 (s, 3 H), 3.86 (s, 3 H), 5.39-5.56 (m, 2 H), 6.61 (d, J = 7.7 Hz, 1 H), 6.63 (s, 1 H), 6.68 (d, J = 3.2 Hz, 2 H), 6.82 (d, J = 7.7 Hz, 1 H). ¹³C NMR (100 MHz, CDCl3): δ = 19.2, 38.4, 55.8, 56.0, 111.1, 112.9, 114.1, 116.0, 121.3, 127.7, 132.0, 132.4, 143.3, 143.7, 144.6, 146.4. IR (KBr): 3384, 3022, 2931, 2835, 1608, 1513, 1460, 1431 cm. MS (EI):
m/z (%) = 274 (100) [M+], 273 (6), 259 (33), 150 (38). HRMS (EI): m/z calcd for C16H18O4: 274.1205; found: 274.1200.