Boronic Acids: New Coupling Partners in Room-Temperature Suzuki Reactions of Alkyl Bromides. Crystallographic Characterization of an Oxidative-Addition Adduct Generated under Remarkably Mild Conditions

Reaction Scheme


Pd(PhCN)2Cl2/P(t-Bu)2 serves as an efficient and a versatile catalyst for room-temperature Sonogashira reactions of aryl bromides.



Pd(PhCN)2Cl2 (11.5 mg, 0.030 mmol) and CuI (3.9 mg, 0.020 mmol; stored under argon or nitrogen) are added to a dry, 4-mL septum-capped vial, which is then sparged with argon and charged with dioxane (1.0 mL; Aldrich Sure/SealTM anhydrous/99.8%). P(t-Bu)3 (260 mL of a 0.25 M solution in dioxane; 0.065 mmol), HN(i-Pr)2 (166 mL, 1.20 mol; Aldrich Sure/SealTM 99.5%), 4-bromoanisole (127 mL, 1.00 mmol), and phenylacetylene (131 mL, 1.20 mmol) are added via syringe to the stirred reaction mixture. During the reaction, precipitation of [H2N(i-Pr)2]Br is observed. After 1.0 hours, the reaction mixture is diluted with EtOAc (5 mL), filtered through a small pad of silica gel (with EtOAc rinsings), concentrated, and purified by flash chromatography (50:1 pentane:EtOAc), which yielded the desired product, 4-methoxyphenyl phenyl acetylene1 (201 mg, 94%).



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