Efficient Synthesis of Bisallylic Ethers from Baylis-Hillman Adducts Promoted by Molecular Iodine

Abstract

A straightforward and efficient synthesis of functionalized ethers from Baylis-Hillman (MBH) adducts was disclosed. In the presence of I₂, MBH adducts underwent smooth dehydration to give a series of bisallylic symmetrical ethers in moderate to good yields.

Key words

Baylis-Hillman adduct - iodine - bisallylation - symmetrical - ether

References and Notes

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8

All new compounds were characterized by ¹H NMR, ¹³C NMR, elemental analysis, and IR spectroscopy.

9

The stereochemistry of product 2 was assigned according to published report.^7d

10

General Procedure for the Synthesis of the Symmetrical Bisallylic Ether
To a stirred solution of Baylis-Hillman adduct 1 (1 mmol) in MeNO₂ (10 mL), I₂ (3 mmol) was added. The resulting mixture was then allowed to react at 80 °C in air. After completion of the reaction, H₂O was added to quench the reaction, and the mixture was successively exacted with Et₂O (3 × 20 mL). The organic phase was washed with sat. Na₂S₂O₃ (15 mL), sat. brine (10 mL), dried over anhyd Na₂SO₄, and filtered. The solvent was removed under reduced pressure to give the crude products, which were purified by column chromatography using EtOAc and petroleum ether as eluent.
Selected Spectroscopy Data of Product 2
Compound 2a (R = Ph): white solid, mp 96.3-97.4 °C. IR (KBr): 3404, 2948, 1714, 1629, 1244, 1006, 768, 694 cm^-1. ¹H NMR (500 MHz, CDCl₃): δ = 7.99 (s, 2 H), 7.63-7.40 (m, 10 H), 4.41 (s, 4 H), 3.87 (s, 6 H) ppm. ¹³C NMR (125 MH_Z, CDCl₃): δ = 168.18, 145.47, 134.83, 130.27, 129.68, 128.78, 128.39, 64.93, 52.40 ppm. MS: m/z (%) = 389 [M + Na]⁺. Anal. Calcd for C₂₂H₂₂O₅: C, 72.13; H, 6.01. Found: C, 72.29; H, 5.97.
Compound 2d (R = 4-ClC₆H₄): white solid, mp 123.1-123.8 °C. IR (KBr): 3408, 1711, 1631, 1237, 816 cm^-1. ¹H NMR (500 MHz, CDCl₃): δ = 7.93 (s, 2 H), 7.57 (d, 4 H, J = 8.5 Hz), 7.41 (t, 4 H, J = 8.5 Hz), 4.36 (s, 4 H), 3.87 (s, 6 H). ¹³C NMR (125 MH_Z, CDCl₃): δ = 167.86, 144.21, 133.95, 133.20, 131.61, 129.12, 128.70, 64.85, 52.53. MS: m/z (%) = 457 [M + Na]⁺. Anal. Calcd for C₂₂H₂₀Cl₂O₅: C, 60.69; H, 4.59. Found: C, 60.63; H, 4.76.