Iodine-Promoted Metal-Free Head-to-Tail Dimerization of Styrenes Affording 1,3-Diarylbut-1-enes

Abstract

A convenient and efficient iodine-mediated head-to-tail dimerization of styrenes to produce the corresponding dimers in the presence of triethyl phosphite is reported. The advantages of the present protocol are metal-free conditions, short reaction time, simplicity, and high efficiency.

Key words

styrenes - arenes - dimerization - iodine - mediate

• References and Notes

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• 10 Typical Experimental Procedure for the Synthesis of Compound 2a P(OEt)₃ (0.20 mmol, 33.2 mg) was added to a solution of 1a (0.20 mmol, 20.8 mg) and I₂ (0.40 mmol, 101.2 mg) in DCE (1 mL), and the reaction mixture was stirred under reflux conditions for 5–30 min. After completion of the reaction, the reaction mixture was diluted with EtOAc, and quenched with sat. Na₂S₂O₃ solution and extracted twice with EtOAc (3 × 15 mL). The organic layer was washed with H₂O and dried over anhydrous Na₂SO₄. The solvent was evaporated in vacuo, and the residue was subjected to column chromatography using EtOAc in PE as the eluent to afford the target compound 2a. (E)-But-1-ene-1,3-diyldibenzene (2a)^6a Colorless oil; yield: 16.2 mg (78%). ¹H NMR (400 MHz, CDCl₃): δ = 7.37–7.18 (m, 10 H), 6.41 (d, J = 4.0 Hz, 2 H), 3.66–3.63 (m, 1 H), 1.47 (d, J = 8.0 Hz, 3 H). 1,1,3-Trimethyl-3-phenyl-2,3-dihydro-1H-indene (2m)^6h Colorless oil; yield: 18.4 mg (78%). ¹H NMR (400 MHz, CDCl₃): δ = 7.28–7.11 (m, 9 H), 2.43 (d, J = 12.0 Hz, 1 H), 2.20 (d, J = 12.0 Hz, 1 H), 1.69 (s, 3 H), 1.35 (s, 3 H), 1.03 (s, 3 H).