BINEPINES: chiral binaphthalene-core monophosphepine ligands for multipurpose asymmetric catalysis

Abstract

The atropisomeric structure of 4,5-dihydro-3H-dinaphtho[2,1-c;1',2'-e]phosphepine is the common axially chiral scaffold of a library of monophosphine ligands nicknamed BINEPINES that have shown a quite remarkable stereoselection efficiency in a broad variety of enantioselective reactions involving the formation of new C-H or C-C or C-X bonds. In this critical review the properties and scope of this type of chiral ligands are illustrated (70 references).

Stereospecific synthesis and catalytic activity of l-histidylidene metal complexes

“…To this end, the formed silylether II was hydrolysed with methanolic TFA and the corresponding alcohol was analysed by chiral HPLC (Table 3). As expected from the remote 25 position of the stereocentre, the histidylidene ligand did not induce any enantioselectivity, neither at room temperature nor at -18 °C (entries 1, 4). In contrast, complexes 6 and 9 containing (S)-Ph-binepine as an enantiopure phosphine ligand generated a moderate 30% enantiomeric excess (ee) in the product alcohol 30 (entries 2, 3).…”

“…This higher selectivity is in agreement with recent 20 mechanistic studies which propose the bonding of the substrate ketone to a silylene-rhodium dihydride species as a critical step. 32 According to such a model, keto-enol tautomerisation and ensuing formation of the silylenolether side product strongly depends on the Lewis acidity of the silicon atom and thus 25 indirectly on the electronic properties of the rhodium centre. Electron-rich neutral rhodium centres as in 5 and 8 increase the electron density at the silylene and hence facilitate substrate bonding in its tautomeric enol form.…”

“…4 Slight modifications are generally required to introduce a metal-carbon bond and to access this area of bioorganometallic chemistry. 5 Peptides are a particularly versatile class of precursors, 6 since the chiral amino acid building 25 blocks are readily available. In addition, the different side chain functionalities allow a variety of modifications and linkages to classical organometallic ligands to be introduced.…”

Highly Modular C1‐Symmetric Chiral (P,N) Ligands with a Stereolabile P Center: Experimental and Theoretical Studies

“…This is especially surprising with regard to the historical developments of homogeneous asymmetric catalysis and the ever-growing catalogue of P-based chiral ligands and organocatalysts. [8] A plausible explanation might be that the well-established configurational stability of P-stereogenic tertiary phosphines has been exploited to prepare robust rather than stereoflexible chiral ligands, despite the difficulty associated with their stereoselective preparation.…”

Complementary Catalytic Strategies to Access ?-Chiral Aldehydes

“…[13] It distinguishes itself by a highly modular scaffold possessing three elements of chirality: i) the axial chirality of the elementary binepine core; [14] ii) a central chirality at a benzylic position; iii) a phosphorus stereogenic center. The latter two elements are stereoselectively installed by introduction of the methylpyridyl unit according to a strategy already employed by Wildhalm and Zhang.…”