Stereoisomeric Tris-BINOL-Menthol Bulky Monophosphites: Synthesis, Characterisation and Application in Rhodium-Catalysed Hydroformylation

Abstract

Four stereoisomeric monoether derivatives, based on axially chiral (R)- or (S)-BINOL bearing a chiral (+)- or (−)-neomenthyloxy group were synthesised and fully characterised by NMR spectroscopy and X-ray crystallography. The respective tris-monophosphites were thereof prepared and fully characterised. The coordination ability of the new bulky phosphites with Rh(CO)2(acac), was attested by 31P NMR, which presented a doublet in the range of δ = 120 ppm, with a 1J(103Rh-31P) coupling constant of 290 Hz. The new tris-binaphthyl phosphite ligands were further characterised by DFT computational methods, which allowed us to calculate an electronic (CEP) parameter of 2083.2 cm−1 and an extremely large cone angle of 345°, decreasing to 265° upon coordination with a metal atom. Furthermore, the monophosphites were applied as ligands in rhodium-catalysed hydroformylation of styrene, leading to complete conversions in 4 h, 100% chemoselectivity for aldehydes and up to 98% iso-regioselectivity. The Rh(I)/phosphite catalytic system was also highly active and selective in the hydroformylation of disubstituted olefins, including (E)-prop-1-en-1-ylbenzene and prop-1-en-2-ylbenzene.

Iridium–phosphine ligand complexes as an alternative to rhodium-based catalysts for the efficient hydroformylation of propene

“…For the hydroformylation catalyzed by Rh-based complexes, the most widely utilized ligand is the phosphine compound (Scheme 1). 9–32 Hence, we mainly focused on the Ir-based catalysts with different monodentate and bidentate ligands. The phosphine ligands are listed in Scheme 2, including the following: triphenylphosphine ( L1 ), tri(4-methoxyphenyl)phosphine ( L2 ), diphenyl( n -propyl)phosphine ( L3 ), tri( n -butyl)phosphine ( L4 ), tri(3-pyridyl)phosphine ( L5 ), di(3-pyridyl)phenylphosphine ( L6 ), diphenyl(3-pyridyl)phosphine ( L7 ), tri(4-methoxypyridyl)phosphine ( L8 ), tri(4- N , N -dimethyl-pyridyl)phosphine ( L9 ); diphenylphosphinomethane ( L10 ), 1,3-bis(diphenylphosphino)propane ( L11 ), 1,4-bis(diphenylphosphino)butane ( L12 ), 1,5-bis(diphenylphosphino)pentane ( L13 ), 1,6-bis(diphenylphosphino)hexane ( L14 ), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene ( L15 ), and tris(2-pyridyl)phosphine ( L16 ).…”

“…Since Rh-based catalysts were applied to olefin hydroformylation by Evans et al , 8 the research on Rh-based catalysts for the hydroformylation of olefin has achieved great progress. 9–34 Compared to the first-generation Co-based catalysts, which typically operate at reaction temperatures of up to 160 °C and under high reaction pressure of 10 MPa, 35,36 and Ru-based catalysts with low activity and poor selectivity for aldehydes, 37,38 Rh-based catalysts have incomparable advantages in olefin hydroformylation, such as mild reaction conditions (80–120 °C and below 3 MPa) and high selectivity for aldehydes (>98%). 19,39–45 Consequently, a significant number of research studies have been directed towards the modification of Rh catalysts.…”

Hydrosilylation of Carbonyl Compounds Catalyzed by Iridium(I) Complexes with (−)‐Menthol‐Based Phosphorus(III) Ligands

“…Among numerous examples of phosphorous-based ligands, especially attractive are ligands with naturally occurring moieties due to their abundance in biomass, providing lower synthesis costs, high activity, and a wide range of chiral substances of natural origin, such as menthol. [50] (À )-Menthol, monoterpenoid, occurring in various mint family plants, is a non-expensive building block in the synthesis of ligands, applied in a variety of catalytic reactions e. g., hydroformylation, [51] hydroarylation, [52] Buchwald-Hartwig amination, [53] and Suzuki-Miyaura coupling. [53] Based on our experience in the field of catalytic hydrometallation processes, [54][55][56][57][58][59][60][61][62][63][64] we sought a new and efficient catalytic system composed of an iridium metal center and menthol-based ligands in the hydrosilylation of carbonyl compounds which would greatly expand the current state of knowledge in the iridium-catalyzed hydrosilylation of carbonyl compounds (Scheme 1).…”