Efficient Condensation between Glyoxal Hydrates and Sulfonium Salts Leading to Highly Functionalized 1,4-Diketones

Abstract

α-Alkylthio-substituted α,β-unsaturated 1,4-dicarbonyl compounds with three different functionalities are easily available through condensation of sulfonium salts and various aromatic or aliphatic glyoxal hydrates catalyzed by Na₂SeO₃ or a combination of selenium dioxide and Na₂CO₃.

Key words

alkenes - catalysis - condensation - sulfur - selenium

References and Notes

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9

Typical Procedure for Preparing Compound 3
A mixture of 1a (152 mg, 1.0 mmol), 2a (261 mg, 1.0 mmol), SeO₂ (4.4 mg, 0.04 mmol), and Na₂CO₃ (10.6 mg, 0.1 mmol) in MeCN (10 mL) was stirred for 4.5 h at r.t. After complete consumption of starting material (TLC), MeCN was removed in vacuum to give yellow syrup. The residue was extracted with CH₂Cl₂ (2 × 30 mL). The combined organic layers were washed with brine (10 mL) and dried over anhyd Na₂SO₄. The extracts were then concentrated under reduced pressure, and the residue was purified by column chromatography (eluent: PE-EtOAc) on SiO₂ to give an 81% yield of 3a [(Z)-3a, 129 mg; (E)-3a, 100 mg].
Compound (Z)-3a: ^¹H NMR (400 MHz, CDCl₃): δ = 8.08 (d, J = 8.5 Hz, 2 H), 7.95 (d, J = 8.5 Hz, 2 H), 7.69-7.44 (m, 6 H), 7.10 (s, 1 H), 2.17 (s, 3 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 191.9, 188.2, 160.6, 137.8, 134.9, 134.8, 132.7, 130.0, 129.1, 128.6, 128.1, 116.0, 15.4. IR (KBr): ν = 2926, 1670, 1635, 1596, 1537, 1246, 1023, 699 cm^-¹.
Compound (E)-3a: ^¹H NMR (400 MHz, CDCl₃): δ = 8.00 (d, J = 8.0 Hz, 2 H), 7.89 (d, J = 8.0 Hz, 2 H), 7.57-7.43 (m, 6 H), 7.04 (s, 1 H), 2.45 (s, 3 H). ^¹³C NMR (100 MHz, CDCl₃): δ = 193.7, 185.1, 160.8, 137.2, 134.9, 133.6, 133.0, 128.8, 128.7, 128.6, 128.4, 115.8, 14.9. IR (KBr): ν = 3413, 1674, 1637, 1540, 1220, 781, 703, 632 cm^-¹. Spectral data were in agreement with those previously reported.^³