General procedure for the synthesis of naphthalene, 1,1'-dinaphthylphosphine oxide, and tris(1-naphthyl)phosphine from 1-bromonaphthalene: To an anhydrous and degassed solution of t-BuOK (8.14 g, 72.5 mmol) in DMSO (73 mL), purged with argon and saturated with dry phosphine, an anhydrous DMSO solution of 1-bromonaphthalene (10.01 g, 48.3 mmol) was obtained ( 7 mL dropwise at 70 °C) for 1 h under stirring and continuous drumming of phosphine. The reaction mixture was heated in a stream of phosphine (70 °C) for 0.5 h. The supply of phosphine was stopped, but the mixture was stirred continuously for 1.5 h (70 °C). In the 31P NMR spectrum of the reaction mixture, the following signals were observed: -62.03 (d, 1JPH 227 Hz) for 1-Np2PH, -33.37 (s) for 1-Np3P, and -2.49 (t, 1JPH 463 Hz) for 1-NpP(O)H2, in a ratio of ~5:1.5:0.1. Trace amounts of 1,2 -Np2PH (-49.78 ppm) and 1,1,2-Np3P (-22.70 ppm). The mixture was then purged with argon, cooled and diluted with cold water (80 mL) to give a white precipitate (1.15 g). The latter was filtered out, washed with water (5 x 30 mL) and Et2O (3 x 25 mL) and dried in air to give 1-Np3P (0.68 g). The filtrate was sequentially extracted with Et2O (50 mL) and CH2Cl2 (2 × 50 mL). (a) The ether extract was washed with cold water (3 × 20 mL), dried with K2CO3, and the solvent was removed under reduced pressure to give a white waxy crude product (5.51 g), which was heated at 1 Torr (100-150 °C, sand bath) to sublimate naphthalene (1.37 g) and distill unreacted BrNp (0.95 g, 91% conversion). The residue was dissolved in EtOH (22 mL) and a white precipitate was filtered out, washed with EtOH (10 × 5 mL) and dried in vacuum to give an emulsion solid (0.62 g, 1-Np3P). After removal of the solvent and drying in vacuum, secondary phosphine oxide 1-Np2P(O)H (2.30 g) was isolated from the alcoholic extract. (b) The CH2Cl2 extract was washed with brine (10% aqueous, KCl), the orange precipitate was filtered out, dried with K2CO3, and the solvent was removed to give a white waxy product (1.21 g). The latter was heated at 1 torr (100-150 °C, sand bath) to sublimate naphthalene (0.17 g), and the residue was washed with EtOH (3 × 20 mL), 1-Np3P (0.08 g) was filtered out, and 1-Np2P(O)H (0.65 g) was removed by EtOH. the total yield of 1-Np2P(O)H was 2.95 g (45%). the total yield of 1-Np3P was 1.38g (23%). The yield of naphthalene was 1.54 g (27%).
