A convenient, selective synthesis of bis[2,4-bis(trifluoromethyl)phenyl]phosphane - Derivatives starting from 1,3-bis(trifluoromethyl)benzene

摘要

The reaction of the sterically shielded phosphane derivative, dichlorodiethylaminophosphane, Cl2PNEt2, with an excess of a mixture of 2,6-bis(ti-ifluoromethyl) and 2,4-bis(trifluoromethyl)-phenyl lithium gives bis[2,4-bis(trifluoromethyl)phenyl]diethylaminophosphane, [2,4-(CF3)(2)C6H3](2)PNEt2, in 72% yield as a colourless solid, while 2,6-bis(trifluoromethyl)phenyl lithium remains unchanged in solution. The amino derivative crystallizes in the monoclinic space group P2(1)/c (a 869.2(1), b 1857.4(1), c 1357.6(1) pm, beta 100.57(4)degrees, Z = 4). Treatment of [2,4-(CF3)(2)C6H3](2)PNEt2 in CHCl3 solution with conc. HCl allows the synthesis of [2,4-(CF3)(2)C6H3)](2)PCl, [2,4-(CF3)(2)C6H3](2)PCl reacts with H2O in THF solution with quantitative formation of the corresponding secondary phosphane oxide. To obtain bis[2,4-bis(trifluoromethyl)phenyl]phosphinic acid, [2,4-(CF3)(2)C6H3](2)P(O)OH, quantitatively, a CHCl3 solution of [2,4-(CF3)(2)C6H3](2)P(O)H, has to be stirred in an NO2 atmosphere. The phosphinic acid crystallizes is the triclinic space group P (1) over bar (a 754.2(1), b 927.6(2), c 1305.5(2) pm, alpha 85.11(2)degrees, beta 75.45(1)degrees, gamma 79.99(2)degrees, Z = 2). From the reaction of the phosphinic acid with either elemental sodium or with cyanide salts, the corresponding phosphinate salts are obtained in an almost quantitatively yield.