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Synlett 2006(18): 2935-2940  
DOI: 10.1055/s-2006-948174
LETTER
© Georg Thieme Verlag Stuttgart · New York

Synthesis of (E)-1-Aryl Alk-1-en-3-ones by Tetraphosphine/Palladium-Catalysed Heck Reactions of Alk-1-en-3-ones with Aryl Bromides

Mhamed Lemhadri, Henri Doucet*, Maurice Santelli*
UMR 6180 CNRS and Université d"Aix-Marseille III, ‘Chirotechnologies: catalyse et biocatalyse’, Laboratoire de Synthèse Organique, Faculté des Sciences de Saint Jérôme, Université d’Aix-Marseille III, Avenue Escadrille Normandie-Niemen, 13397 Marseille Cedex 20, France
Fax: +33(4)91983865; e-Mail: henri.doucet@univ-cezanne.fr; e-Mail: m.santelli@univ-cezanne.fr;
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Publication History

Received 27 March 2006
Publication Date:
04 August 2006 (online)

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Abstract

The tetraphosphine cis,cis,cis-1,2,3,4-tetrakis(di­phenylphosphinomethyl)cyclopentane in combination with [Pd(C3H5)Cl]2 affords a very efficient catalyst for the Heck reaction of alk-1-en-3-ones with aryl bromides. If appropriate reaction ­conditions are used (NaOAc as base, hydroquinone as stabilising agent and DMF as solvent) high yields of (E)-1-aryl alk-1-en-3-one derivatives are obtained. In general, higher reaction rates were observed with electron-poor aryl bromides, but the electron-rich aryl bromides 4-N,N-dimethylaminobromobenzene and 4-bromoanisole also led to the arylated enones. Even with sterically very congested aryl bromides such as 9-bromoanthracene, 2,4,6-trimethylbromo­benzene or 2,4,6-triisopropylbromobenzene, the expected (E)-1-aryl alk-1-en-3-ones were obtained in moderate to good yields. Moreover, several reactions can be performed with as little as 0.1% catalyst.

Key words

Tedicyp - Heck reaction - (E)-1-aryl alk-1-en-3-one derivatives

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DMF 99.8%, sodium acetate 99%, aryl halides and alk-1-en-3-ones were not purified before use. All reactions were run under argon in Schlenk tubes. As a typical experiment, the reaction of aryl halide (1 mmol), alk-1-en-3-one (2 or 4 mmol, see Table [1] and Table [2] ), hydroquinone (9 mg, 0.08 mmol) and NaOAc (164 mg, 2 mmol) at 110 °C during 20 h in dry DMF (3 mL) with cis,cis,cis-1,2,3,4-tetrakis(diphenylphosphinomethyl)cyclopentane-0.5[PdCl(C3H5)]2 complex under argon affords the corresponding (E)-1-aryl alk-1-en-3-one after addition of H2O (20 mL), extraction with CH2Cl2 (20 mL), separation, drying (MgSO4), evaporation and purification by chromatography on silica gel.

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All new compounds gave satisfactory 1H NMR, 13C NMR and elemental analyses. 1H (300 MHz), 13C NMR (75 MHz) in CDCl3 and elemental analyses of selected products: compound 9: 1H NMR: δ = 9.09 (s, 1 H), 8.26 (s, 1 H), 8.11 (d, J = 8.5 Hz, 1 H), 7.85 (d, J = 8.5 Hz, 1 H), 7.75 (t, J = 7.8 Hz, 1 H), 7.66 (d, J = 16.1 Hz, 1 H), 7.58 (t, J = 7.8 Hz, 1 H), 6.94 (d, J = 16.1 Hz, 1 H), 2.44 (s, 3 H). 13C NMR: δ = 197.7, 149.3, 139.7, 135.7, 130.8, 129.5, 128.4, 128.3, 127.6, 127.5, 127.4, 127.0, 27.9. Anal. Calcd for C13H11NO (197): C, 79.16; H, 5.62. Found: C, 79.42; H, 5.69.
Compound 20: 1H NMR: δ = 7.78 (d, J = 16.4 Hz, 1 H), 7.02 (s, 2 H), 6.23 (d, J = 16.4 Hz, 1 H), 3.08 (sept, J = 6.8 Hz, 2 H), 2.88 (sept, J = 6.8 Hz, 1 H), 2.70 (q, J = 7.4 Hz, 2 H), 1.28-1.12 (m, 21 H). 13C NMR: δ = 200.6, 148.9, 146.3, 142.0, 132.6, 130.4, 120.8, 34.3, 34.1, 30.2, 24.0, 23.9, 8.1. Anal. Calcd for C20H30O (286): C, 83.86; H, 10.56. Found: C, 84.02; H, 10.78.
Compound 25: 1H NMR: δ = 8.19 (d, J = 8.3 Hz, 2 H), 7.67 (d, J = 8.3 Hz, 2 H), 7.53 (d, J = 16.5 Hz, 1 H), 6.80 (d, J = 16.5 Hz, 1 H), 2.64 (t, J = 7.4 Hz, 2 H), 1.69 (sext, J = 7.4 Hz, 2 H), 0.94 (t, J = 7.4 Hz, 3 H). 13C NMR: δ = 199.7, 148.5, 140.8, 139.0, 129.5, 128.7, 124.1, 43.3, 17.5, 13.7. Anal. Calcd for C12H13NO3 (219): C, 65.74; H, 5.98. Found: C, 65.61; H, 6.12.
Compound 27: 1H NMR: δ = 7.49 (d, J = 16.0 Hz, 1 H), 7.43 (d, J = 8.4 Hz, 2 H), 6.67 (d, J = 8.4 Hz, 2 H), 6.55 (d, J = 16.0 Hz, 1 H), 3.01 (s, 6 H), 2.60 (t, J = 7.4 Hz, 2 H), 1.69 (sext, J = 7.4 Hz, 2 H), 0.96 (t, J = 7.4 Hz, 3 H). 13C NMR: δ = 200.7, 151.8, 143.2, 130.0, 122.2, 121.6, 111.8, 42.4, 40.1, 18.2, 13.9. Anal. Calcd for C14H19NO (217): C, 77.38; H, 8.81. Found: C, 77.19; H, 8.80.