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Synlett 2010(2): 231-234  
DOI: 10.1055/s-0029-1219164
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Concurrent α-Iodination and N-Arylation of Cyclic β-Enaminones

Yan Chen, Tong Ju, Junwei Wang, Wenquan Yu, Yunfei Du*, Kang Zhao*
Tianjin Key Laboratory for Modern Drug Delivery & High Efficiency, School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, P. R. of China
Fax: +86(22)27890968; e-Mail: duyunfeier@tju.edu.cn; e-Mail: kangzhao@tju.edu.cn;
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Publication History

Received 28 October 2009
Publication Date:
22 December 2009 (online)

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Abstract

A variety of N-substituted 3-aminocyclohex-2-enones were converted into the corresponding N-arylated α-iodo enaminones in high yields via concurrent α-iodination and N-arylation mediated by ArI(OAc)2. A mechanism is postulated to account for the reaction differences between the cyclic and the acyclic β-enamin­ones, which undergo predominant α-acetoxylation under the same reaction conditions.

Key words

polyvalent iodine compounds - α-iodination - PIDA - α-iodo enaminones - 3-aminocyclohex-2-enones

    References and Notes

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3

Compound 3a
Crystallized in the monoclinic space group P2 (1)/c with cell dimensions: a = 10.497 (2) Å, b = 13.607 (3) Å, c = 11.987 (2) Å, α = 90˚, β = 114.36 (3)˚, γ = 90˚, V = 1559.9 (5) ų, D c  = 1.657 g/cm³, Z = 4. CCDC: 753753.

14

General Procedure for α-Iodination and N-Arylation of β-Enaminones
To a solution of substrate 1 (1.0 mmol) in dried DCE (10 mL) was added dropwise a solution of aryliodine diacetate 2 (1.3 mmol) in dried DCE (10 mL) at 60 ˚C under nitrogen atmosphere. After the addition, the reaction mixture was stirred at this temperature until the conversion was complete as indicated by TLC. Then the mixture was cooled to r.t., treated with sat. aq NaHCO3 (40 mL) and extracted with CH2Cl2 (3 × 20 mL). The combined organic layer was dried over Na2SO4 and evaporated under reduced pressure to remove the solvent. The residue was purified by column chromatography using a mixture of PE and EtOAc as eluent to afford the product.
Compound 3a: yellow solid, mp 106-108 ˚C. ¹H NMR (500 MHz, CDCl3): δ = 7.32 (t, J = 7.9 Hz, 4 H), 7.14 (t, J = 7.4 Hz, 2 H), 7.02 (d, J = 7.7 Hz, 4 H), 2.75-2.65 (m, 2 H), 2.58 (t, J = 6.0 Hz, 2 H), 2.04-1.91 (m, 2 H). ¹³C NMR (100 MHz, CDCl3): δ = 193.09, 166.95, 145.20, 129.52, 125.45, 125.22, 95.80, 37.54, 34.04, 21.38. ESI-LRMS: m/z = 390.2 [M + H+].
Compound 5a: yellow solid, mp 102-104 ˚C. ¹H NMR (400 MHz, DMSO): δ = 7.51 (dd, J = 4.8, 2.5 Hz, 3 H), 7.35 (dd, J = 7.7, 1.9 Hz, 2 H), 2.43 (s, 3 H), 2.35 (s, 3 H), 2.22 (s, 3 H). ESI-LRMS: m/z = 271.9 [M + K+]. The spectroscopic data for all the new compounds could be found in the Supporting Information.