Stereoisomeric Tris-BINOL-Menthol Bulky Monophosphites: Synthesis,Characterisation and Application in Rhodium-Catalysed Hydroformylation |
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| Authors: | Alexandre P. Felgueiras,Fá bio M. S. Rodrigues,Rui M. B. Carrilho,Pedro F. Cruz,Vitor H. Rodrigues,Tamá s Ké gl,Lá szló Kollá r,Mariette M. Pereira |
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| Affiliation: | 1.Coimbra Chemistry Centre, Department of Chemistry, University of Coimbra, Rua Larga, 3004-535 Coimbra, Portugal; (A.P.F.); (F.M.S.R.); (P.F.C.);2.Centre for Physics of the University of Coimbra, Department of Physics, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal;3.Department of Inorganic Chemistry and ELKH-PTE Research Group for Selective Chemical Syntheses, University of Pécs, Ifjúság útja 6, H-7624 Pécs, Hungary; (T.K.); (L.K.) |
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| 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. |
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| Keywords: | BINOL, menthol, X-ray diffraction, monophosphite synthesis, Mitsunobu reaction, DFT computational methods, Tolman’ s cone angle, computed electronic parameter (CEP), rhodium-catalysed hydroformylation |
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