Carboranylphosphites—new effective ligands for rhodium-catalyzed asymmetric hydrogenation of dimethyl itaconate

Chiral phosphites derived from carboranes: Electronic effect in catalytic asymmetric hydrogenation

“…Catalytic performance of the new ligands 3-8, as well as carboranylphosphites 1, 2 obtained by us earlier, 3 was initially explored in the enantioselective Rh-catalyzed hydrogenation reaction of methyl 2-acetamidoacrylate 10 (Scheme 3). The results of the Rh-catalyzed hydrogenation reactions are summarized in Table 1.…”

“…The use of the corresponding 9-ortho-and 9-meta-carborane derived ligands (1, 2) produced dimethyl succinate 13 with excellent enantioselectivity (99.8-99.7% ee). 3 Introduction of the electron-withdrawing 3-ortho-carboranyl group (ligand 3, Table 2, entry 3) slightly lowered ee. Further increasing the electron-acceptor character of the carboranyl substituent (ligand 4, Table 2, entry 4) led to a strong decrease of the enantioselectivity (65% ee).…”

“…3 We believe, that the easy preparation of the chiral monodentate phosphites, their outstanding activity and selectivity in asymmetric synthesis, [4][5][6] in combination with the modular nature of carboranes, make such series of ligands ideally suited for an exhaustive search of an optimal structure for enantioselective catalysis. No less important is that, due to the constant steric effect of all dicarba-closo-dodecaborane isomers, the influence of the electronic properties of the exocyclic substituent R (Scheme 1) on the enantioselectivity and conversion in the asymmetric process may be clearly studied.…”

Synthesis of tervalent phosphorus esters in biphasic system using potassium phosphate as unique solid base

“…Novel monodentate phosphites, containing ortho-and meta-closododecarboranyl groups, have been synthesized and applied in the asymmetric Rh-catalyzed hydrogenation of dimethyl itaconate [16]. Using chiral binaphtholic phosphite, a highly enantioselective rhodium-catalyzed addition of arylboronic acids to N-tosylarylimines is described [17].…”

Carborane-derived diphosphites: New ligands for Pd-catalyzed allylic amination

“…Pesticide, bactericide and ferment-inhibition properties of the compounds were also known [2,3]. Despite the encouraging performance of many achiral carborane organophosphorus ligands, especially phosphines [4,5], chiral phosphorus derivatives of carboranes are rare and represented only by our recent work related to the synthesis and first successful application of chiral phosphite derivatives of carboranes in the asymmetric hydrogenation of prochiral olefins (up to 99.8% ee) [6,7]. Encouraged by excellent enantioselectivities in the asymmetric hydrogenation processes and motivated by our continuing efforts in the design of novel chiral carboranylphosphite ligands, we have prepared a series of sterically congested carborane-phosphite derivatives for an application in other important asymmetric catalytic transformations, namely Pd-catalyzed allylic substitution.…”