27954-98-9Relevant articles and documents
Calix[4]arene-diphosphite rhodium complexes in solvent-free hydroaminovinylation of olefins
Monnereau, Laure,Semeril, David,Matt, Dominique
supporting information; experimental part, p. 1670 - 1673 (2010/12/24)
Under solvent-free conditions rhodium complexes containing hemispherical diphosphites based on a calix[4]arene skeleton catalyse efficiently the hydroaminovinylation of α-olefins, thereby leading to high proportions of linear enamines/amines (when startin
Highly regioselective hydroformylation with hemispherical chelators
Semeril, David,Matt, Dominique,Toupet, Loic
experimental part, p. 7144 - 7155 (2009/08/07)
The hemispherical diphosphites (R,R)- or (S,S)-5,11,17,23-tetratert-butyl- 25,27-di(OR)-26,28-bis(1,1′-binaphthyl-2,2′-dioxyphosphanyloxy) -calix[4]arene (R = OPr, OCH2Ph, OCH2-naphtyl, O-fluorenyl; R = H, R' = OPr) (LR), all with C2 symmetry, have been synthesised starting from the appropriate di-O-alkylated calix[4]-arene precursor. In the presence of [Rh(acac)(CO)2], these ligands straightforwardly provide chelate complexes in which the metal centre sits in a molecular pocket defined by two naphthyl planes related by the C 2 axis and the two apically situated R groups. Hydroformylation of octene with the LPr/Rh system turned out to be highly regioselective, the linear-to-branched (l:b) aldehyde ratio reaching 58:1. The l:b ratio significantly increased when the propyl groups were replaced by -CH 2Ph (l:b = 80) or -CH2naphthyl (1:b = 100) groups, that is, with substituents able to sterically interact with the apical metal sites, but without inducing an opening of the cleft nesting the catalytic centre. The trend to preferentially form the aldehyde the shape of which fits with the shape of the catalytic pocket was further confirmed in the hydroformylation of styrene, for which, in contrast to catalysis with conventional diphosphanes, the linear aldehyde was the major product (up to ca. 75 % linear aldehyde). In the hydroformylation of frarts-2-octene with the Lbenzyl/ Rh system, combined isomerisation/hydroformylation led to a remarkably high 1:b aldehyde ratios of 25, thus showing that isomerisation is more effective than hydroformylation. Unusually large amounts of linear products were also observed with all the above diphosphites in the tandem hydroformylation/amination of styrene (1:b of ca. 3:1) as well as in the hydroformylation of allyl benzyl ether (1:b ratio up to 20).
