Synthesis of electron-withdrawing butane- and arene-sulfonylamino phosphines and use in rhodium-catalyzed hydroformylation

Reaction of RSO2N(H)CH2CH2N(H)SO2R [R = Bu (1), 4-nitrobenzene (7), 1-naphthalene (9a), 2-naphthalene (9b)] with PhPCl2 or EtPCl2 gives monodentate phosphorus compounds 2 and 3(R = Bu, PhP and EtP), and 8(R = 4-nitrobenzene, PhP), and with Ph2PCl gives the corresponding bidentate phosphine ligands Ph2PN(SO2R) CH2CH2N(SO2R)PPh2 [R = Bu (10), 4-nitrobenzene (11), 1- and 2-naphthalene (12a,b)]; similar reactions of N,N(1-butanesulfonyl)-2,2-diaminobiphenyl (4) give monodentate 5(PhP) and 6(EtP) and N,N-bis (diphenylphosphino)-N,N-(1-butanesulfonyl)-2,2-diaminobiphenyl (16). A monodentate analogue of 10 was also prepared, Ph2PN(Et)SO2Bu (14). Diphosphorus compounds with two butanesulfonylamino groups on phosphorus were also prepared from 1 and Cl2P(CH2)nPCl2(n = 2, 4) to give 19 and 20. Details of the 13C NMR false AAX systems are reported for 19 and 20. Rhodium-catalyzed hydroformylation reactions were run at 60 and 80 °C, at CO/H2 pressures from 4–11 atm, and in THF, toluene, CH2Cl2, and dioxane. Results show that the highest ratios of linear (n) to branched (iso) aldehydes were obtained with arenesulfonamides (niso > 10) while the bidentate alkanesulfonamide 10 gave a lower niso ratio of 7.2 but the highest rate [k1 = 1.98 h–1, turnover frequency = 1130 mol aldehyde (mol Rh)–1 h–1] in THF at 80 °C. Both the rate and niso ratio for 10 were found to increase with decreasing CO/H2 pressure in THF and in toluene, although the rate change was small for toluene. Both the rate and niso ratio for 10 also increased in CH2Cl2, but this was found not to be due to lower CO/H2 concentrations in solution, on the basis of solubility measurements in THF and CH2Cl2.