Palladium-Catalyzed Negishi Cross-Coupling of Arylzinc Reagents with Functionalized Vinylic Tellurides

Abstract

The Negishi cross-coupling reaction of arylzinc chlorides and bromides with functionalized vinylic tellurides in the ­presence of a catalytic amount of PdCl₂ in THF at room temperature is described. This cross-coupling reaction is general and permits the synthesis of functionalized substituted alkenes in good yields and high stereoselectivity.

Key words

palladium - vinylic tellurides - organozinc - tellurium - Negishi

References and Notes

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13

The arylzinc reagents were prepared in situ by the reaction of aryl halides with n-BuLi in THF followed by addition of ZnCl₂.

14

Typical Procedure for Cross-Coupling Reaction.
A 25 mL, two-necked, round-bottom flask equipped with a magnetic stir bar, rubber septum and argon was charged sequentially with PdCl₂ (0.035 g, 0.2 mmol), CuI (0.19 g,
1 mmol), THF (1 mL) and 1,2-bis(organoylchalcogeno)al-kene (1a, 0.328 g, 1 mmol). Then, phenylzinc chloride (2a,
3 mmol), previously prepared in another flask was trans-ferred via cannula at r.t. The black mixture was stirred at r.t. and the reaction time was determined monitoring the reaction by TLC. The reaction mixture was then quenched with aqueous NH₄Cl (30 mL), washed with CH₂Cl₂ (3 × 20 mL), dried with MgSO₄ and the solvent removed under vacuum. The products were purified by column chromatography. Selected spectral and analytical data for 3a: yield: 0.180 g (82%). ¹H NMR: (200 MHz, CDCl₃):
δ = 7.39-7.24 (m, 5 H), 5.93 (s, 1 H), 2.43 (t, J = 6.76 Hz, 2 H), 2.22 (s, 3 H), 1.33-1.28 (m, 6 H), 0.85 (t, J = 6.32 Hz, 3 H) ppm. ¹³C NMR: (100 MHz, CDCl₃): δ = 140.05, 139.35, 128.05, 127.92, 127.01, 123.41, 38.66, 31.30, 28.13, 22.39, 17.85, 13.98 ppm.