Einfacher Zugang zu 2-Alkylsuccinaten durch asymmetrische katalytische Hydrierung von durch Stobbe-Kondensation erhaltenen Itaconaten

Abstract

Im 500‐g‐Maßstab sind enantiomerenreine 2‐Alkylsuccinate leicht zugänglich, wenn bei der Hydrierung kationische Rh‐Komplexe mit tetraalkylsubstituierten 1,2‐Bis(phospholanyl)ethan‐ oder ‐benzol(R′‐DuPHOS)‐Liganden verwendet werden [Gl. (a)]. Selbst Gemische der prochiralen (E)‐ und (Z)‐Isomere von Itaconaten werden hocheffizient und enantioselektiv umgesetzt, z. B. auch tetrasubstituierte Itaconate mit 96% ee. R′ = H, Alkyl, Aryl.

Synthesis of Chiral Heterocyclic Phosphines for Application in Asymmetric Catalysis

“…Noteworthy is the high competency for i-Pr-BPE for the Ru-catalyzed hydrogenation of N,N,N',N'- -ketoesters including its own precursor ("self breeding process") [58]. 2-Alkylsuccinates with enantioselectivities of 97-99 %ee could be synthesized by asymmetric hydrogenation of substituted itaconates with [Rh(COD)(EtDuPHOS)]BF 4 as a precatalyst and 5.5 bar initial hydrogen pressure [97]. BPE and DuPHOS ligands were also employed in the asymmetric hydrogenation of prochiral Nacyl enamides to give acetylated amines in 92-99 %ee [98].…”

Chiral 1,1′-Diphosphetanylferrocenes: New Ligands for Asymmetric Catalytic Hydrogenation of Itaconate Derivatives

“…[8] Subsequently, the diols were converted to 1,3-diol cyclic sulfates 3 through treatment with thionyl chloride followed by Ru-catalyzed oxidation with sodium periodate. [11] The small absorption band which is revealed in the calculated spectrum of the dimer at longer wavelengths indicates a small deviation from parallelism, see M. Kasha, H. R. Rawls, M. Ashraf El-Bayoumi, Pure Appl. A wide range of different 2,4-disubstituted FerroTANE ligands may be obtained through this procedure.…”

Chiral 1,1′-Diphosphetanylferrocenes: New Ligands for Asymmetric Catalytic Hydrogenation of Itaconate Derivatives

“…[10] VPO measurements (concentration range from 1 to 5 mmol L À1 in dioxane at 608C using benzil for calibration) afforded a molecular weight of 950 for compound 1 h (calculated for dimer: 955.4). [11] The small absorption band which is revealed in the calculated spectrum of the dimer at longer wavelengths indicates a small deviation from parallelism, see M. Kasha, H. R. Rawls, M. Ashraf El-Bayoumi, Pure Appl. Chem.…”

“…The results of these studies (Table 1) reveal that cationic catalysts bearing the Et-FerroTANE and Pr-FerroTANE ligands (1 b and 1 c, respectively), are very effective for this transformation, affording the product 5 with enantioselectivity comparable to that achieved with the Et-DuPHOS-Rh catalyst (97 % ee). [11] Striking is the difference observed between results achieved with the FerroTANE ligands 1 a ± e and the structurally analogous 1,1'-bis(2,5-dialkylphospholanyl)ferrocene derivatives [3b] 6 a (alkyl Me) and 6 b (alkyl Et) (entries 6 ± 7). The advantages conferred by the phosphetane ligands are evident, although the reason for such a significant increase in selectivity upon moving from a five-to a four-membered phosphorus heterocycle is unclear at present.…”

“…The BPPM-Rh and analogous catalysts previously were considered the best available for this transformation. [13c] Surprisingly, the EtDuPHOS-Rh catalyst, which is so effective for hydrogenation of a wide range of Stobbe-derived itaconate derivatives, [11] was …”