Air Stable Diaminophosphine Oxide Ligands for Transition Metal Catalyzed Cross-Coupling Reactions

These air stable diaminophosphine oxide ligands find effective use¹⁾ in palladium-catalyzed Suzuki type reactions of readily available but potentially difficult and challenging aryl chloride substrates.¹⁾

The ligands facilitate the activation of C-F bonds in the Ni-catalyzed Kumada cross coupling reaction²⁾ and exhibit superior catalytic activity as compared to all earlier known protocols.

These sophisticated ligands provide a competent alternative to the use of traditional palladium/triarylphosphane catalysts as well as electron rich alkyl-substituted tertiary phosphines and secondary phosphine oxides in transition metal catalyzed cross coupling reactions.

Typical procedure: ²⁾
A solution of [Ni(acac)₂] (7 mg, 0.03 mmol, 3 mol%) and diaminophosphine oxide 2 (13 mg, 0.03 mmol, 3 mol%) in dry THF (0.5 mL) is stirred for 10 min at ambient temperature under N₂. 1-Fluoronaphthalene (148 mg, 1.01 mmol) is added, and the solution is stirred for 5 min. Thereafter, 4-methoxyphenylmagnesium bromide (0.5 M in THF, 3.0 mL, 1.50 mmol) is added. The resulting dark solution is stirred at ambient temperature for 15 h. Et₂O (75 mL) and H₂O (75 mL) are added to the reaction mixture. The separated aqueous phase is extracted with Et₂O (75 mL×2). The combined organic layers are dried over MgSO₄ and concentrated in vacuo. The remaining residue is purified by column chromatography on silica gel (n-pentane/Et₂O, 300:1→100:1) to yield 4-(1-naphthyl)anisole as a pale yellow solid (223 mg, 94%).