A Novel Coupling Reaction of Allenyl Carbinols with Aldehydes Mediated by InCl₃ via a 1,3-Transposition of Oxygen

Abstract

A new procedure for the synthesis of β-hydroxy enones from allenyl carbinols and aldehydes is described. The use of InCl₃ to promote reaction results in a mild and convenient protocol for the preparation of β-hydroxy enones.

Key words

aldehydes - allenes - coupling - enones - indium

References

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10

General Procedure: To a solution of indium(III)chloride (1.1 equiv) and benzaldehyde (1.5 equiv) in CH₂Cl₂ was added drop-wise octa-1,2-dien-4-ol (1 equiv) in CH₂Cl₂ at 20 °C. After stirring for 5 h at 20 °C, aq NaHCO₃ was added to the reaction mixture. The aqueous layer was extracted with Et₂O (2×). After drying the combined organic solution over anhyd Na₂SO₄, the solvents were removed under reduced pressure. Fresh column chromatography (SiO₂, 10% EtOAc in hexanes) afforded 3a in 73% yield. IR(neat): ν = 3444, 2922, 1628 cm^-1. ¹H NMR (500 MHz, CDCl₃): δ = 0.91 (t, 3 H, J = 7.3 Hz), 1.34 (m, 2 H), 1.44 (m, 2 H), 2.23 (m, 2 H), 2.96 (d, 2 H, J = 6.2 Hz), 3.55 (d, 1 H, J = 3.1 Hz), 5.20 (m, 1 H), 6.11 (dt, 1 H, J = 1.7, 16.0 Hz), 6.87 (dt, 1 H, J = 7.0, 16.0 Hz), 7.32 (m, 5 H). ¹³C NMR (125 MHz, CDCl₃): δ = 200.7, 149.7, 143.2, 130.8, 128.7, 127.8, 125.9, 70.3, 48.4, 32.5, 30.3, 22.5, 14.0. HRMS calcd for C₁₅H₂₀O₂: 232.1463. Found: 232.1460.