Synlett 2006(10): 1511-1514  
DOI: 10.1055/s-2006-944202
LETTER
© Georg Thieme Verlag Stuttgart · New York

Efficient Synthesis of (E)-3-Alkylidene-2(3H)-furanones from 3-(1-Hydroxy­alkyl)-2-silyloxyfurans

John Boukouvalas*, Olivier Marion
Département de Chimie, Université Laval, Quebec City, Quebec G1K 7P4, Canada
Fax: +1(418)6567916; e-Mail: john.boukouvalas@chm.ulaval.ca;
Further Information

Publication History

Received 16 February 2006
Publication Date:
12 June 2006 (online)

Abstract

Several unsubstituted (E)-3-alkylmethylidene- and (E)-3-(arylmethylidene)-2(3H)-furanones have been synthesized in highly stereoselective fashion by mesylation-elimination of 3-(1-hydoxyalkyl)-2-silyloxyfurans. The latter were prepared from 2-triisopropylsilyloxy-3-bromofuran by halogen-lithium exchange and reaction of the in situ generated 3-lithiated silyloxyfuran with aldehydes.

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Data for 10: colorless liquid. 1H NMR (400 MHz, CDCl3): δ = 1.10 (18 H, d, J = 7.2 Hz), 1.29 (3 H, m), 6.27 (1 H, d, J = 2.4 Hz), 6.80 (1 H, d, J = 2.4 Hz). 13C NMR (100 MHz, CDCl3): δ = 12.3, 17.4, 73.3, 114.1, 131.7, 153.4. HRMS: m/z calcd: 318.0651 [M+]; found: 318.0656.

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Typical Procedure.
To a solution of bromofuran 10 (0.720 g, 2.26 mmol) in anhyd THF (30 mL) stirred at -78 °C under nitrogen was added n-BuLi (2.5 M in hexane, 1.08 mL, 2.49 mmol). After 30 min at -78 °C, a solution of freshly distilled n-hexanal (0.450 g, 4.53 mmol) in THF (10 mL) was added dropwise and the mixture was stirred at -78 °C for 2 h. Then, H2O was added (150 mL) and the solution was extracted twice with EtOAc. The combined extracts were washed with H2O, aq sat. NaCl, dried (Na2SO4) and concentrated in vacuo. Purification by flash chromatography (95:5:1, hexane-Et2O-Et3N) afforded furylcarbinol 11a (0.708 g, 92%). All furylcarbinols 11a-j were obtained as oils and characterized by 1H NMR, 13C NMR, and HRMS; data for representative compounds are provided below.
Data for 11a: 1H NMR (300 MHz, CDCl3): δ = 0.87-1.80 (32 H, m), 2.17 (1 H, m), 4.60 (1 H, m), 6.27 (1 H, d, J = 1.9 Hz), 6.76 (1 H, d, J = 1.9 Hz). 13C NMR (75 MHz, CDCl3): δ = 12.0, 14.0, 17.7, 22.7, 25.6, 31.7, 37.4, 65.9, 99.7, 109.7, 131.3, 152.3. HRMS: m/z calcd: 297.1886 [M - C3H7]+; found: 297.1891.
Data for 11e: 1H NMR (400 MHz, CDCl3): δ = 1.07 (18 H, m), 1.27 (3 H, m), 2.05 (1 H, d, J = 3.0 Hz), 5.75 (1 H, d, J = 3.0 Hz), 6.12 (1 H, d, J = 2.4 Hz), 6.71 (1 H, d, J = 2.4 Hz), 7.30 (5 H, m). 13C NMR (100 MHz, CDCl3): δ = 12.5, 17.8, 67.9, 99.9, 110.5, 126.2, 127.3, 128.5, 131.6, 143.8, 153.5. HRMS: m/z calcd: 346.1964 [M+]; found: 346.1961.
Data for 11f: 1H NMR (400 MHz, CDCl3): δ = 1.08 (18 H, m), 1.27 (3 H, m), 2.17 (1 H, d, J = 3.6 Hz), 3.73 (3 H, s), 5.71 (1 H, s), 6.16 (1 H, d, J = 2.2 Hz), 6.71 (1 H, d, J = 2.2 Hz), 6.85 (2 H, d, J = 8.4 Hz), 7.31 (2 H, d, J = 8.4 Hz). 13C NMR (100 MHz, CDCl3): δ = 12.5, 17.8, 55.4, 67.6, 100.1, 110.6, 113.8, 127.5, 131.6, 136.2, 153.3, 158.9. HRMS: m/z calcd: 333.1522 [M - C3H7 +]; found: 333.1518.
Data for 11g: 1H NMR (400 MHz, CDCl3): δ = 1.08 (18 H, m), 1.26 (3 H, m), 2.42 (1 H, br s), 5.81 (1 H, s), 6.04 (1 H, d, J = 2.2 Hz), 6.71 (1 H, d, J = 2.2 Hz), 7.54 (2 H, d, J = 9.1 Hz), 8.14 (2 H, d, J = 9.1 Hz). 13C NMR (100 MHz, CDCl3): δ = 12.5, 17.8, 67.0, 98.9, 110.0, 123.7, 126.9, 132.1, 147.2, 151.3, 153.8. HRMS: m/z calcd: 392.1893 [MH+]; found: 392.1890.

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The E-stereochemistry of compounds 5a-j was determined by NOESY experiments. The Z-isomers of 5a-c are clearly distinguished by 1H NMR from their E-isomers by the upfield shift of the three olefin protons (Δδ ca. 0.1-0.3 ppm).

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Typical Procedure.
To a solution of furylcarbinol 11e (0.190 g, 0.55 mmol) in anhyd CH2Cl2 (5 mL) stirred at -78 °C under nitrogen was added Et3N (0.056 g, 0.55 mmol) and MsCl (0.063 g, 0.55 mmol). The mixture was stirred at -78 °C for 1 h and TBAF (1.0 M in THF, 0.55 mL, 0.55 mmol) was added. The mixture was slowly warmed to r.t. with stirring over 1 h. Purification by column chromatography (4:1, hexane-Et2O) provided furanone 5e (0.088 g, 93%).
Data for 5a: colorless oil. 1H NMR (400 MHz, CDCl3): δ = 0.86 (3 H, t, J = 7.1 Hz), 1.28 (4 H, m), 1.48 (2 H, m), 2.31 (2 H, m), 6.12 (1 H, dd, J = 4.0, 1.0 Hz), 6.74 (1 H, m), 6.94 (1 H, m). 13C NMR (100 MHz, CDCl3): δ = 14.1, 22.6, 28.3, 30.7, 31.6, 105.4, 126.2, 144.1, 145.4, 168.3. HRMS: m/z calcd: 166.0994 [M+]; found: 166.0991.
Data for 5b: colorless oil. 1H NMR (400 MHz, CDCl3): δ = 0.95 (6 H, d, J = 6.8 Hz), 1.85 (1 H, m), 2.24 (2 H, t, J = 6.4 Hz), 6.15 (1 H, dd, J = 3.6, 0.8 Hz), 6.78 (1 H, m). 13C NMR (100 MHz, CDCl3): δ = 22.7, 38.6, 39.7, 105.5, 126.9, 143.0, 145.6, 168.3. HRMS: m/z calcd: 152.0837 [M+]; found: 152.0842.
Data for 5c: colorless oil. 1H NMR (400 MHz, CDCl3): δ = 1.11 (6 H, d, J = 6.4 Hz), 2.70 (1 H, m), 6.15 (1 H, dd, J = 3.6, 0.8 Hz), 6.61 (1 H, dq, J = 10.0, 0.8 Hz), 6.97 (1 H, m). 13C NMR (100 MHz, CDCl3): δ = 22.2, 30.5, 105.4, 124.1, 145.4, 150.0, 168.8. HRMS: m/z calcd: 138.0681 [M+]; found: 138.0676.
Data for 5d: colorless oil. 1H NMR (400 MHz, CDCl3): δ = 1.22 (9 H, s), 6.34 (1 H, dd, 3.8, 0.8 Hz), 6.77 (1 H, dd, J = 1.9, 0.8 Hz), 6.99 (1 H, dd, J = 3.8, 1.9 Hz). 13C NMR (100 MHz, CDCl3): δ = 29.9, 35.6, 105.8, 122.4, 145.4, 153.7, 169.9. HRMS: m/z calcd: 152.0837 [M+]; found: 152.0833.
Data for 5e: yellow solid, mp 190-192 °C. 1H NMR (400 MHz, CDCl3): δ = 6.58 (1 H, dd, J = 3.6, 1.0 Hz), 7.12 (1 H, dd, J = 3.6, 2.0 Hz), 7.43 (4 H, m), 7.53 (2 H, m). 13C NMR (100 MHz, CDCl3): δ = 106.4, 123.3, 129.3, 130.4, 130.8, 134.8, 137.9, 147.5, 169.6. HRMS: m/z calcd: 172.0524 [M+]; found: 172.0519.
Data for 5f: yellow solid, mp 129-130 °C. 1H NMR (400 MHz, CDCl3): δ = 3.83 (3 H, s), 6.55 (1 H, dd, J = 3.4, 0.8 Hz), 6.92 (2 H, dd, J = 7.0, 1.8 Hz), 7.08 (1 H, dd, J = 3.4, 2.0 Hz), 7.37 (1 H, m), 7.51 (2 H, dd, J = 7.0, 2.0 Hz).
13C NMR (100 MHz, CDCl3): δ = 55.7, 106.4, 114.9, 120.7, 127.6, 132.4, 137.8, 146.5, 161.9, 170.1. HRMS: m/z calcd: 202.0630 [M+]; found: 202.0624.
Data for 5g: yellow solid, mp 212-213 °C. 1H NMR (400 MHz, CDCl3): δ = 6.55 (1 H, dd, J = 3.7, 1.0 Hz), 7.25 (1 H, dd, J = 3.7, 1.6 Hz), 7.44 (1 H, m), 7.68 (2 H, dd, J = 6.9, 1.6 Hz), 8.28 (2 H, dd, J = 6.9, 1.6 Hz). 13C NMR (100 MHz, CDCl3): δ = 106.0, 124.5, 126.7, 130.7 (2×), 134.1, 140.8, 149.8, 168.5. Anal. Calcd for C12H7NO4: C, 60.83; H, 3.25; N, 6.45. Found: C, 60.56; H, 3.05; N, 6.38.
Data for 5h: yellow solid, mp 92-93 °C. 1H NMR (400 MHz, CDCl3): δ = 6.55 (1 H, dd, J = 3.5, 0.8 Hz), 7.17 (1 H, dd, J = 3.5, 1.8), 7.40 (4 H, m), 7.51 (1 H, m). 13C NMR (100 MHz, CDCl3): δ = 106.2, 124.6, 128.5, 129.8, 130.6 (2×), 135.3, 135.9, 136.5, 148.3, 169.1. HRMS: m/z calcd: 206.0135 [M+]; found: 206.0129.
Data for 5i: yellow solid, mp 222-223 °C. 1H NMR (400 MHz, CDCl3): δ = 6.63 (1 H, dd, J = 3.4, 0.8 Hz), 7.15 (1 H, dd, J = 3.4, 1.8 Hz), 7.44 (4 H, m), 7.64 (6 H, m). 13C NMR (100 MHz, CDCl3): δ = 106.5, 123.1, 127.3, 127.9, 128.4, 129.2, 131.0, 133.8, 137.4, 140.0, 143.5, 147.4, 169.7. Anal. Calcd for C17H12O2: C, 82.24; H, 4.87. Found: C, 81.97; H, 4.66.
Data for 5j: yellow solid, mp 191-192 °C (dec.). 1H NMR (400 MHz, CDCl3): δ = 6.55 (1 H, dd, J = 3.4, 1.6 Hz), 6.80 (2 H, m), 7.07 (1 H, dd, J = 3.4, 1.6 Hz), 7.12 (1 H, m), 7.63 (1 H, d, J = 1.6 Hz). 13C NMR (100 MHz, CDCl3): δ = 108.1, 113.4, 119.3, 120.3, 122.1, 146.0, 146.8, 151.9, 169.9. HRMS: m/z calcd: 162.0317 [M+]; found: 162.0322.