An Atom-Economical and Environmentally Benign Preparation of ­Unsymmetrical Bis-allyl Ethers via Dimerization of Baylis-Hillman Adducts Catalyzed by Cesium Hydroxide Monohydrate

Abstract

Promoted by a catalytic amount of cesium hydroxide monohydrate, unsymmetrical bis-allyl ethers consisting of an E-allylic unit and a terminal allylic unit were formed via dimerization of Baylis-Hillman adducts in moderate to good yields at room temperature.

cesium hydroxide monohydrate - unsymmetrical bis-allyl ethers - Baylis-Hillman adduct - stereoselectivity - dimerization

References

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12

Typical Experimental Procedure. In a 25-mL flask was charged with CsOH·H₂O (50 mg, 0.3 mmol) and THF (10 mL). The suspension was stirred at r.t. for 10 min. The Baylis-Hillman adduct 1 (1 mmol) was added to the flask and stirred at r.t. for 0.5-1 h. The reaction mixture was poured into Et₂O (50 mL), washed with H₂O (2 × 25 mL) and brine (35 mL). The combined ethereal layers were dried over MgSO₄. After evaporation of solvent the residue was purified by chromatography using cyclohexane-EtOAc (6:1) as eluent.

13

Spectroscopic data of 2b: oil. ¹H NMR (400 MHz, CDCl₃): δ = 2.34 (s, 3 H, CH ₃), 2.37 (s, 3 H, CH ₃), 3.71 (s, 3 H, OCH ₃), 3.79 (s, 3 H, OCH ₃), 4.20 (d, 1 H, ² J = 10.0 Hz, methylene-H), 4.33 (d, 1 H, ² J = 10.0 Hz, methylene-H), 5.35 (s, 1 H, O-CH-Ar), 6.00 (t, 1 H, ² J = 1.6 Hz, terminal olefin-H), 6.35 (t, 1 H, ² J = 1.6 Hz, terminal olefin-H), 7.13 (d, 2 H, J = 8.0 Hz, ArH), 7.15 (d, 2 H, J = 8.0 Hz, ArH), 7.27 (d, 2 H, J = 8.0 Hz, ArH), 7.39 (d, 2 H, J = 8.0 Hz, ArH), 7.87 (s, 1 H, ArCH=). ¹³C NMR (400 MHz, CDCl₃): δ = 21.16, 21.39, 51.74, 51.97, 63.72, 79.28, 125.53, 127.81, 128.93, 129.18, 129.97, 131.80, 136.29, 137.60, 139.63, 140.84, 143.24, 144.95, 166.42, 168.15. IR (film): ν = 3073, 3025, 1721, 1631, 1594, 1066 cm^-1. MS (70 eV): m/z (%) = 394 [M⁺]. Anal. Calcd for C₂₄H₂₆O₅: C, 73.08; H, 6.64. Found: C, 73.25; H, 6.70. According to NOESY experiment, there is no NOE correlation between the signals of the internal olefin proton and the allylic methylene protons.

14

Selected spectroscopic data for compound 2:
Compound 2a: oil. ¹H NMR (400 MHz, CDCl₃): δ = 3.69 (s, 3 H, OCH ₃), 3.80 (s, 3 H, OCH ₃), 4.23 (d, 1 H, ² J = 10.0 Hz, methylene-H), 4.34 (d, 1 H, ² J = 10.0 Hz, methylene-H), 5.33 (s, 1 H, OCH-Ph), 5.90 (t, 1 H, ² J = 1.2 Hz, terminal-olefin-H), 6.31 (t, 1 H, ² J = 1.2 Hz, terminal-olefin-H), 7.25-7.51 (m, 10 H, ArH), 7.91 (s, 1 H, ArCH=). IR (film): ν = 3078, 3030, 1720, 1633, 1600, 1067 cm^-1. MS (70 eV): m/z (%) = 366 [M⁺]. Anal. Calcd for C₂₂H₂₂O₅: C, 72.12; H, 6.05. Found: C, 72.25; H, 6.01.
Compound 2c: oil. ¹H NMR (400 MHz, CDCl₃): δ = 3.70 (s, 3 H, OCH ₃), 3.80 (s, 3 H, OCH ₃), 4.20 (d, 1 H, ² J = 10.0 Hz, methylene-H), 4.29 (d, 1 H, ² J = 10.0 Hz, methylene-H), 5.34 (s, 1 H, O-CH-Ar), 5.94 (t, 1 H, ² J = 1.2 Hz, terminal-olefin-H), 6.36 (t, 1 H, ² J = 1.2 Hz, terminal-olefin-H), 7.29-7.36 (m, 6 H, ArH), 7.41 (d, 2 H, J = 8.0 Hz, ArH), 7.85 (s, 1 H, ArCH=). ¹³C NMR (400 MHz, CDCl₃): δ = 51.80, 52.08, 63.56, 78.79, 125.90, 128.43, 128.74, 129.11, 131.09, 131.36, 132.95, 133.80, 135.54, 137.83, 140.52, 143.54, 166.05, 167.58. IR (film): ν = 3070, 3026, 1724, 1632, 1593, 1118 cm^-1. MS (70 eV): m/z (%) = 434 [M⁺], 436 [M⁺ + 2]. Anal. Calcd for C₂₂H₂₀Cl₂O₅: C, 60.70; H, 4.63. Found: C, 60.56; H, 4.69.
Compound 2d: oil. ¹H NMR (400 MHz, CDCl₃): δ = 3.74 (s, 3 H, OCH ₃), 3.82 (s, 3 H, OCH ₃), 4.25 (d, 1 H, ² J = 10.0 Hz, methylene-H), 4.32 (d, 1 H, ² J = 10.0 Hz, methylene-H), 5.76 (t, 1 H, ² J = 1.2 Hz, terminal olefin-H), 5.83 (s, 1 H, O-CH-Ar), 6.41 (t, 1 H, ² J = 1.2 Hz, terminal olefin-H), 7.22-7.42 (m, 6 H, ArH), 7.52-7.63 (m, 2 H, ArH), 8.04 (s, 1 H, ArCH=). ¹³C NMR (400 MHz, CDCl₃): δ = 52.15, 52.40, 64.72, 76.07, 127.08, 127.13, 127.51, 129.21, 129.40, 128.64, 129.73, 130.19, 130.66, 131.19, 131.49, 133.28, 136.88, 139.84, 141.38, 141.83, 166.48, 167.61. IR (film): ν = 3066, 3025, 1721, 1635, 1592, 1067 cm^-1. MS (70 eV): m/z (%) = 434 [M⁺], 436 [M⁺ + 2]. Anal. Calcd for C₂₂H₂₀Cl₂O₅: C, 60.70; H, 4.63. Found: C, 60.64; H, 4.56.
Compound 2e: oil. ¹H NMR (400 MHz, CDCl₃): δ = 3.79 (s, 3 H, OCH ₃), 3.80 (s, 3 H, OCH ₃), 3.81 (s, 3 H, OCH ₃), 3.84 (s, 3 H, OCH ₃), 4.25 (d, 1 H, ² J = 10.0 Hz, methylene-H), 4.34 (d, 1 H, ² J = 10.0 Hz, methylene-H), 5.35 (s, 1 H, O-CH-Ar), 6.01 (t, 1 H, ² J = 1.2 Hz, terminal olefin-H), 6.36 (t, 1 H, ² J = 1.2 Hz, terminal olefin-H), 6.86 (d, 2 H, J = 8.0 Hz, ArH), 6.90 (d, 2 H, J = 8.0 Hz, ArH), 7.32 (d, 2 H, J = 8.0 Hz, ArH), 7.48 (d, 2 H, J = 8.0 Hz, ArH), 7.86 (s, 1 H, ArCH=). IR (film): ν = 3075, 3020, 1721, 1629, 1606, 1120 cm^-1. MS (70 eV): m/z (%) = 426 [M⁺]. Anal. Calcd for C₂₄H₂₆O₇: C, 67.59; H, 6.15. Found: C, 67.40; H, 6.24.

Bis-allyl ethers were found to be useful intermediates in organic synthesis, see:

15a Ben Ammar H. Le Nôtre J. Salem M. Kaddachi MT. Dixneuf PH. J. Organomet. Chem.  2002,  662:  63 

15b Le Nôtre J. Brissieux L. Sémeril D. Bruneau C. Dixneuf PH. Chem. Commun.  2002,  1772