Synthesis
General procedure for the synthesis of bis(3,5-dimethylphenyl)phosphine oxide from 3,5-dimethylbromobenzene: 1-bromo-3,5-dimethylbenzene (129.5 g, 3.5 eq.) was slowly added to a suspension of magnesium shavings (17.0 g, 3.5 eq.) in tetrahydrofuran (THF, 770 mL) while controlling the internal temperature to maintain at 40-50 °C. The reaction mixture was stirred continuously at 40-50 °C for 1 h and subsequently cooled to 0 °C. Triethyl phosphate ((EtO)3PO, 27.7 g, 0.200 mol) was added dropwise over 30 min and stirring was continued for 1 h at 0 °C. Upon completion of the reaction, the reaction was quenched with 6 M aqueous hydrochloric acid (260 mL) and the mixture was extracted with dichloromethane (CH2Cl2, 260 mL x 3) and washed with water (H2O, 130 mL x 2). After concentration under vacuum, the residue was purified by silica gel column chromatography to afford bis(3,5-dimethylphenyl)phosphine oxide (49.7 g, 96% yield) as a light yellow solid.
References
[1] Chemistry Letters, 2013, vol. 42, # 9, p. 1035 - 1037
[2] Chemical Communications, 2013, vol. 49, # 82, p. 9425 - 9427
[3] Patent: WO2014/196930, 2014, A1. Location in patent: Page/Page column 21; 22
[4] Patent: EP1452537, 2004, A1. Location in patent: Page 25
[5] Zeitschrift fur Anorganische und Allgemeine Chemie, 2016, vol. 642, # 6, p. 508 - 514
