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 NN'-(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)(n)PCl2 (n = 2, 4) to give 19 and 20. Details of the C-13 NMR false AA'X systems are reported for 19 and 20. Rhodium-catalyzed hydroformylation reactions were run at 60 and 80degreesC, at CO/H-2 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 (n:iso > 10) while the bidentate alkanesulfonamide 10 gave a lower n:iso ratio of 7.2 but the highest rate [k(1) = 1.98 h(-1), turnover frequency = 1130 mol aldehyde (mol Rh)(-1) h(-1)] in THF at 80degreesC. Both the rate and n:iso ratio for 10 were found to increase with decreasing CO/H, pressure in THF and in toluene, although the rate change was small for toluene. Both the rate and n:iso 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.