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Synlett 2008(1): 55-60  
DOI: 10.1055/s-2007-990924
LETTER
© Georg Thieme Verlag Stuttgart · New York

1,2-Diarylethenyl Sulfones: Readily-Prepared Masked Diarylethynes for Access to Aryleneethynylenes

Takashi Doi, Akihiro Orita*, Daisuke Matsuo, Ryosuke Saijo, Junzo Otera*
Department of Applied Chemistry, Okayama University of Science, Ridai-cho, Okayama 700-0005, Japan
Fax: +81(86)2564292; e-Mail: orita@high.ous.ac.jp; e-Mail: otera@high.ous.ac.jp;
Further Information

Publication History

Received 26 September 2007
Publication Date:
03 December 2007 (online)

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Abstract

1,2-Di(halophenyl)ethenyl phenyl sulfones were prepared readily by successive treatment of halophenylmethyl sulfones with LiHMDS (lithium hexamethyldisilazide), halobenzaldehydes, diethyl chlorophosphate and LiHMDS. The di(halophenyl)ethenyl sulfones thus obtained were transformed successfully to aryleneethynylenes by Sonogashira coupling with arylethyne followed by LiHMDS-promoted elimination of phenylsulfinic acid.

Key words

alkynes - sulfones - aldehydes - eliminations - aryleneethynylenes

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Typical Procedures1-(3-Bromophenyl)-2-(3-iodophenyl)-1-(phenylsulfon-yl)ethene (4a): To a THF solution (30 mL) of 3-bromo-phenylmethyl phenyl sulfone (2.00 g, 6.4 mmol) was added a THF solution of LiHMDS (1.0 M, 7.0 mL, 7.0 mmol) at -78 °C, and the mixture was stirred for 0.5 h. A THF solution (8 mL) of 3-iodobenzaldehyde (1.24 g, 5.3 mmol) was added at -78 °C, and the mixture was stirred for 1 h. Diethyl chlorophosphate (0.75 mL, 5.4 mmol) was added at -78 °C, and the mixture was stirred at r.t. for 1 h. A THF solution of LiHMDS (1.0 M, 5.4 mL, 5.4 mmol) was added at -78 °C, and the mixture was stirred at r.t. overnight. After usual workup with EtOAc-aq NH4Cl, the organic layer was evaporated, and the residue was subjected to column chromatography on silica gel (10% EtOAc-hexane) to furnish 4a (2.24 g, 80%).Compound 4a: E/Z = 88:12 (the geometry of E- or Z-isomers was not determined, several signals overlapped in 13C NMR). 1H NMR (500 MHz, CDCl3): δ = 6.91 (t, J = 7.8 Hz, 1 H), 6.93-7.00, 7.03-7.12 (m, 2 H), 7.13-7.21, 7.32-7.37 (m, 2 H), 7.40-7.68 (m, 8 H), 7.85, 7.88 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 94.1 (93.5), 122.7 (122.1), 128.7, 128.9, 129.1, 129.3, 128.1, 128.5, 128.6, 130.1, 130.4, 129.5, 129.7, 132.5, 132.9, 133.3, 133.6, 134.5, 132.1, 132.7, 133.4, 135.3, 136.4, 138.1, 139.0, 139.6, 137.1, 137.3, 137.6, 139.9, 141.6, 141.7.
1-(3-Bromophenyl)-2-[3-(4-methoxyphenyl-ethynyl)phenyl]-1-(phenylsulfonyl)ethene (5a): A toluene solution (14 mL) of 4a (1.20 g, 2.3 mmol), 4-methoxy-phenylethyne (341 mg, 2.6 mmol), Pd(PPh3)4 (132 mg, 0.11 mmol), CuI (23.0 mg, 0.12 mmol) and diisopropylamine (4.6 mL) was stirred at r.t. for 12 h. After filtration, the filtrate was washed with aq NH4Cl, and the aqueous layer was extracted with EtOAc. The combined organic layer was washed with aq NaCl, dried over MgSO4 and evaporated. The residue was subjected to column chromatography on silica gel (10% EtOAc-hexane) to afford 5a (1.07 g, 88%). Compound 5a: only one isomer was obtained. The geometry E or Z isomer was not determined. 1H NMR (500 MHz, CDCl3): δ = 3.83 (s, 3 H), 6.87 (d, J = 8.9 Hz, 2 H), 6.90 (d, J = 8.2 Hz, 1 H), 6.97 (d, J = 7.9 Hz, 1 H), 7.12 (t, J = 7.8 Hz, 1 H), 7.14-7.18 (m, 2 H), 7.29 (s, 1 H), 7.37-7.46 (m, 5 H), 7.49-7.53 (m, 1 H), 7.57 (t, J = 7.5 Hz, 1 H), 7.64 (d, J = 7.6 Hz, 2 H), 7.94 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ = 55.3, 86.9, 90.4, 114.1, 114.9, 122.6, 124.4, 128.6, 128.7, 128.9, 129.0, 129.5, 130.3, 132.4, 132.6, 132.9, 133.1, 133.2, 133.4, 133.5, 133.9, 137.5, 138.3, 141.0, 159.9.
1-(3-Bromophenylethynyl)-3-(4-methoxyphenyl-ethynyl)benzene (3a): To a toluene solution (22 mL) of 5a (285 mg, 0.54 mmol) was added a THF solution of LiHMDS (1.0 M, 2.2 mL, 2.2 mmol) at 0 °C, and the mixture was stirred at r.t. for 2 h. After usual workup with EtOAc-aq NH4Cl, the organic layer was evaporated, and the residue was subjected to column chromatography on silica gel (2% EtOAc-hexanes) to furnish 3a (161 mg, 77%). Compound 3a: 1H NMR (500 MHz, CDCl3): δ = 3.84 (s, 3 H), 6.89 (d, J = 8.9 Hz, 2 H), 7.23 (t, J = 7.9 Hz, 1 H), 7.33 (t, J = 7.8 Hz, 1 H), 7.43-7.50 (m, 6 H), 7.67-7.70 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ = 55.2, 87.1, 88.2, 89.9, 90.2, 114.0, 115.0, 122.1, 123.0, 124.0, 125.0, 128.4, 129.7, 130.1, 130.9, 131.4, 131.5, 133.1, 134.3, 134.4, 159.7.