A series of P-stereogenic enantiopure 1,2-bis[(aryl)(phenyl)phosphino]ethane ligands was prepared through an extensive systematic incorporation of various substituents onto the P-o-anisyl rings of Knowles' DiPAMP. The study of incidence of such modification on the Rh(I)-catalyzed hydrogenation of alpha-styrene revealed that substitution on position 3 is detrimental, while it is beneficial on position 5. Namely, a 2.5-fold increased catalyst activity coupled with higher enantioselectivity (90%) was attained with the P-(2-MeO-3-naphthyl)-substituted ligand under mild conditions (1 bar H2, rt).
COBISS.SI-ID: 4310298
We disclosed new series of P-stereogenic 1,2-bis[(o-RO-phenyl)(phenyl)phosphino]ethane (R-SMS-Phos) ligands wherein R= various branched hydrocarbon chains. In fact, the methyls of the o-anisyl groups of the DiPAMP ligand were switched to R-groups. The new ligands displayed an increase by several times in reaction rate and were much more enantioselective in the asymmetric hydrogenation of a wide range of olefins. The overall results obtained with ''tBu-SMS-Phos'' ligand are amongst the best ever reported in the Rh-phosphine catalyzed hydrogenation.
COBISS.SI-ID: 4355098
New P-stereogenic 1,2-bis[(o-iso-propoxyphenyl)(phenyl)phosphino]ethane ligand (i-Pr-SMS-Phos) was prepared and tested in Rh-catalyzed asmmetric hydrogenation of olefins. The study of the catalytic profile of Rh-(iPr-SMS-Phos) under different reaction variables was as well carried out. NMR studies of hydrogenation of MAC with this catalyst showed for the first time that the more reactive catalyst-substrate adduct is formed in higher amount than the less reactive adduct in contrary to the usual trend in such catalysis accounting for the obtained higher reaction rates and enantioselectivities.
COBISS.SI-ID: 4320282
We have prepared a series of new ligands, analogues of DiPAMP by incorporating various substituents onto its o-anisyl groups. The new ligands were evaluated in Rh-catalyzed hydrogenation of olefins. The overall performance of these ligands was better than DiPAMP’s: enhanced activities and increased enantioselectivities were obtained in almost all cases, particularly with the P-(2,3,4,5-tetra-MeO-Ph)-substituted ligand which we dubbed ''4MeBigFUS''. This work is useful contribution to the synthesis of P-stereogenic ligands and could result in development of industrial processes.
COBISS.SI-ID: 3807258
The work presents a study of the ring opening of 3,4-dimethyl-2,5-diphenyl-1,3,2-axazaphospholidine-2-borane with sterically hindered arylithium reagents. Several research groups have tackled the subject however their results are not in full agreement with our findings. This shows the high level of difficulty encountered in such chemistry. We believe that our work is an interesting contribution to the field of organic synthesis directed towards the synthesis of P-chiral organophosphorus compounds and it offers new opportunities for designing new phosphine ligands with interesting structures.
COBISS.SI-ID: 3807258