Highly regio- and stereo-selective copolymerization of CO2 with racemic propylene oxide catalyzed by unsymmetrical (S,S,S)-salenCo(III) complexes

Abstract

A novel unsymmetrical (S,S,S)-salen ligand bearing a derived chiral-BINOL was synthesized by the reaction of the condensation product of (1S,2S)-1,2-diaminocyclohexane mono(hydrogen chloride) with 3-adamanyl-5-tert-butyl-2-hydroxybenzaldehyde and 3-formoyl-2-hydroxy-2′-alkyloxy-1,1′-binaphthyl, which originated from (S)-1,1′-bi-2-naphthol via a four-step reaction. The cobalt complexes of this ligand, in conjunction with a nucleophilic cocatalyst, exhibited excellent activity in catalyzing asymmetric, regio-and stereo-selective copolymerization of CO 2 and racemic propylene oxide. The highest record of kinetic resolution coefficient (K rel ) was obtained with the use of binary catalyst system consisting of (S,S,S)-salenCo(III) complex 1c and bulky bis(triphenylphosphine)-iminium chloride (PPNCl). The resulting poly(propylene carbonate)s have more than 99% carbonate linkages and more than 98% head-to-tail content. carbon dioxide, propylene oxide, polycarbonate, stereochemistry, asymmetric catalysis polymerization, kinetic resolution

Microstructure Analysis of a CO2 Copolymer from Styrene Oxide at the Diad Level

“…In a recent publication, we reported a new catalyst system based on unsymmetrical ( S , S , S )‐salenCo III complexes that contained a derived chiral‐BINOL unit (BINOL=1,1′‐bi‐2‐naphthol) for the asymmetric copolymerization of CO 2 and racemic propylene oxide under mild conditions 20. Both the chiral diaminocyclohexane backbone and the S ‐configured 2′‐isopropyloxy‐1,1′‐binaphthyl ligand cooperatively provide a chiral environment around the central metal ion for this reaction.…”

“…[20] Both the chiral diaminocyclohexane backbone and the S-configured 2'-isopropyloxy-1,1'-binaphthyl ligand cooperatively provide a chiral environment around the central metal ion for this reaction. When the unsymmetrical (S,S,S)-salenÀCo III complex with PPNY (PPN = bis(triphenylphosphine)iminium, Y = 2,4-dinitrophenoxide) were tested in the copolymerization of CO 2 and (R)-SO (Figure 3), 92 % enantioselectivity for the R configuration was observed.…”

Stereoregular poly(cyclohexene carbonate)s: Unique crystallization behavior

“…The stereoregularity of the resultant polycarbonate is easily determined by 13 C-NMR spectra of carbonyl region signals or/and the enantiomeric excess (ee) of the corresponding cyclohexane-1,2-diol after hydrolysis with aqueous NaOH. Based on our preliminary studies of the asymmetric alternating copolymerization of aliphatic epoxides and CO 2 [30,31] , we succeeded in designing highly stereoregular catalyst systems regarding unsymmetric enantiomerically pure cobalt(III) complexes, and further synthesized various optically active polycarbonates: all have more than 99% carbonate linkages. 13 C-NMR spectra in carbonyl region of the stereoregular PCHCs demonstrate their isotactic structure, with the near disappearance of the syndiotactic diads (δ = 153.3-151.1, see Supporting Information, Fig.…”

Perfectly Alternating Copolymerization of Propylene Oxide and CO2over SalenCo/SalenCr Complexes

“…The selectivity to carbonate linkage/ether linkage as well as polymeric carbonate/ cyclic carbonate in the product, the ring-opening regiochemistry of epoxides during the copolymerization process (24) and regularity of the polycarbonate have been paid much attention and concerns. Among all the catalysts, the homogeneous catalysts of metal-salen complexes seem to be very promising and having significant advantages over traditional heterogeneous catalysts (25)(26)(27).…”