Electron Withdrawing Substituents on Equatorial and Apical Phosphines Have Opposite Effects on the Regioselectivity of Rhodium Catalyzed Hydroformylation

Abstract

The electronic effects of electron withdrawing aryl substituents on equatorial and apical diphosphines were investigated. Chelating diphosphines designed to coordinate in diequatorial or in apical−equatorial positions were synthesized, and their effects on the regioselectivity of rhodium catalyzed 1-hexene hydroformylation were observed. Only diequatorial coordination was observed for 2,2‘-bis[(diphenylphosphino)methyl]-1,1‘-biphenyl (BISBI) complexes (BISBI)Ir(CO)2H (8) and [BISBI-(3,5-CF3)]Ir(CO)2H (10), and only apical−equatorial coordination was seen for 1,2-bis(diphenylphosphino)ethane (DIPHOS) complexes (DIPHOS)Ir(CO)2H (14) and [DIPHOS-(3,5-CF3)]Ir(CO)2H (15). For the trans-1,2-bis[(diphenylphosphino)methyl]cyclopropane (T-BDCP) complexes, a mixture of diequatorial and apical−equatorial complexes was seen. For (T-BDCP)Ir(CO)2H (12), 12-ae was favored over 12-ee by 63:37, but for [T-BDCP-(3,5-CF3)]Ir(CO)2H (13) the conformational preference was reversed and a 10:90 ratio of 13-ae:13-ee was seen. The electron withdrawing groups in the equatorial positions of BISBI-(3,5-CF3) (1) and T-BDCP-(3,5-CF3) (2) led to an increase in n-aldehyde regioselectivity in rhodium catalyzed hydroformylation. However, electron withdrawing aryl substituents in the apical positions of DIPHOS-(3,5-CF3) (3) led to a decrease in n-aldehyde regioselectivity in rhodium catalyzed hydroformylation.

Rhodium-Biphephos-Catalyzed Tandem Isomerization–Hydroformylation of Oleonitrile

“…In a typical experiment, the desired amount of Rh(acac)(CO) 2 .72 mmol) in the desired solvent (7 mL) was added onto the resulting mixture. The solution was transferred under argon into a 90 mL or 45 mL stainless-steel autoclave under argon equipped with a magnetic stir bar.…”

“…A combination of Rh(acac)(CO) 2 and Biphephos promotes the tandem isomerizationhydroformylation of the long-chain fatty oleonitrile. The possibility to obtain linear aldehydes starting from this substrate was confirmed, highlighting the influence of the overall and relative pressures and of temperature.…”

“…The synthesis of linear aldehydes is of high interest for industrial purposes, and very high regioselectivities (l/b > 99:1) have been achieved from terminal alkenes with rhodium catalysts using bulky bisphosphine (e.g., Bisbi [2] and Naphos [3]) and bisphosphite (e.g., Biphephos [4]) ligands. However, the selective formation of linear aldehydes is much more challenging when starting from internal alkene as, in this case, preliminary isomerization of the C=C bond is necessary to bring it to the terminal position before performing the hydroformylation process itself.…”

Ligand modified real heterogeneous catalysts for fixed-bed hydroformylation of propylene

“…In spite of the high level of implemented commercial processes, their practical applications have been limited by difficulties in achieving industrially viable catalyst-product separation [3]. A series of studies of this catalyst system led to an understanding of the factors that govern reactivity and selectivity [4]: -donor ligands may inhibit the reaction completely, switching to stronger -acceptor ligands such as phosphites leading to more active and more selective hydroformylation catalysts [5][6][7][8].…”

Selective hydroformylation of alkyl acrylates using [2,2′-bis(dipyrrolylphosphinooxy)-1,1′-(±)-binaphthyl]/Rh catalyst: reversal of regioselectivity

“…31,32 In a certain range, catalysts with larger cone angle were in favor of forming ee isomers which will lead to higher l/b ratio. For L1 and L5, the cone angle is 99 and 113 respectively, 2,33 and their bidentate ee-coordination in trigonal bipyramidal [HRhL(1 or 5)(CO) 2 ] seems to be the preferred isomer.…”