Tetrahydrofuran → 3-Phosphino benzothiophene

Participants

Reaction Steps

Under a nitrogen atmosphere a three necked 1 L flask was charged with diethyl ether (200 ml) and a solution of LiAlH4 in THF (58 mL of 1 N solution, 58 mmol). A solution of 3-bis(chloro)phosphino benzo[d]thiophene (18.24 g, 77.6 mmol) in ether (ca. 40 mL) was added dropwise over ca. 30 minutes. An exothermic reaction took place, and a solid formed. The excess LiAlH4 was hydrolyzed by the dropwise addition of NaOH (15 ml 4 N solution) which led to the formation of a colourless solid which precipitated readily. The supernatant was removed via cannula, and the solid was extracted with another 20 ml of ether. Evaporation of the solvent in vacuo left the crude phosphine as a mobile oil which was further purified by vacuum destillation. Yield: 11.31 g (87%), b.p. 93° C., 0.036 mbar. 1H-NMR (C6D6, 300 MHz) δ 3.59 (dd, 2 H, 1JP,H=200.5 Hz, 4J=1.2 Hz, PH2); 7.10 (“tr”, 1 H, J=7.4 Hz, H-6); 7.19 (“dtr”, 2JH,P=7.5 Hz, 4J=1.2 Hz, H-2); 7.20 (tr, 1 H, J=7.4 Hz, H-5); 7.57 (d, 1 H, J=7.5 Hz, H-7); 7.70 (d, 1 H, J=7.5 Hz, H-4). 13C-NMR (C6D6, 75 MHz) δ 122.06 (d, J=16.1 Hz, C-2); 122.693 (C-7); 123.72 (C-4); 124.60, 124.63 (C-5, C-6), 134.54 (d, J=35 Hz, C-2); 140.75 (d, J=2.6 Hz, C-8); 142.22 (d, J=2 Hz, C-9). 31P{1H}-NMR (C6D6, 121 MHz) δ−163.1.

Provenance & Evidence