1454866-39-7Relevant academic research and scientific papers
Exploring steric effects in diastereoselective synthesis of chiral aminophenolate zinc complexes and stereoselective ring-opening polymerization of rac-lactide
Wang, Haobing,Yang, Yang,Ma, Haiyan
, p. 7356 - 7372 (2016)
A series of tridentate chiral aminophenol proligands and corresponding zinc complexes, LZnX (L = (S)-2-{[(1-R4-2-pyrrolidinyl)CH2N(R3)-]CH2}-6-R1-4-R2-C6H2O, X = N(SiMe3)2, R3 = nBu, R4 = Bn: R1 = R2 = Cl (1), R1 = R2 = Me (2), R1 = R2 = tBu (3); X = N(SiMe3)2, R1 = trityl, R2 = Me: R3 = n-octyl, R4 = Bn (4), R3 = Bn, R4 = Bn (5), R3 = nBu, R4 = naphthalen-1-ylmethyl (6), R3 = nBu, R4 = iPr (7); R1 = R2 = cumyl, R3 = Et, R4 = Bn: X = N(SiMe3)2 (8), X = OtBu (9), X = Et (10), X = Cl (11)), have been synthesized. Complexes 4, 6, and 11 were obtained as enantiopure products (4 and 6 as enantiopure a; 11 as enantiopure b), while complexes 1-3, 5, and 7-10 as a pair of diastereomers, but in different ratios, which have been proved by X-ray diffraction and NMR spectroscopic studies. When exposed to the ring-opening polymerization of rac-lactide, most of these complexes can effectively produce PLAs with narrow polydispersities, desirable molecular weights, and moderate to high isotacticities. The structure-selectivity relationships, including the relationships of structure-synthesis diastereoselectivity and structure-polymerization stereoselectivity, have been further investigated. Consistent trends of diastereoselectivity and stereoselectivity are observed with the variations of the R1 group at the ortho-position of the phenolate ring and the R3 group in the pyrrolidinyl moiety. The decrease of the steric bulkiness of the R4 group on the central amine has less influence on the diastereoselectivity, but leads to considerable loss of the stereoselectivity, whereas the decrease of the steric bulkiness of the X group results in a reverse of the diastereoselectivity, but shows no influence on the stereoselectivity. There is probably no direct relationship between the diastereoselectivity in complex synthesis and the stereoselectivity of the complex toward the ROP of rac-LA. The stereocontrol of these complexes might largely rely on the substituents in the ligand framework rather than their diastereomer ratios.
Diastereoselective synthesis of chiral aminophenolate magnesium complexes and their application in the stereoselective polymerization of: Rac -lactide and rac -β-butyrolactone
Wang, Haobing,Guo, Jianshuang,Yang, Yang,Ma, Haiyan
, p. 10942 - 10953 (2016)
A series of magnesium silylamido complexes supported by chiral aminophenolate ligands were synthesized, and their catalytic behaviors toward the ring-opening polymerization of rac-lactide (LA) and rac-β-butyrolactone (BBL) were explored. The reactions of Mg[N(SiMe3)2]2 with chiral tridentate aminophenols L1-10H [L = (S)-{[(1-R4, 2-pyrrolidinyl)CH2N(R3)-]}CH2-(6-R1-4-R2)-C6H2O-] in a 1:1 molar ratio in toluene gave the chiral aminophenolate magnesium silylamido complexes L1-10MgN(SiMe3)2 as enantiopure compounds or as pairs of diastereomers. As determined by X-ray analysis, structures a and b of diastereomer mixtures adopt the configuration of SCSNRNRMg-a and SCSNSNSMg-b, respectively. It was found that most of these magnesium complexes served as highly active initiators for the ring-opening polymerization of rac-LA. Besides, the stereoselectivity of chiral magnesium complexes gradually changed from isoselective-biased (Pm = 0.67) to heteroselective-enriched (Pr = 0.81) via a stepwise adjustment of the substituents of the ligand framework. It was noted that, as the rare reported active magnesium initiator for the ROP of rac-BBL, complexes 3-9 can efficiently initiate the ring-opening polymerization of rac-BBL in a controlled manner, giving moderate syndiotactic (Ps up to 0.73) PHBs.
Highly diastereoselective synthesis of chiral aminophenolate zinc complexes and isoselective polymerization of rac-lactide
Wang, Haobing,Ma, Haiyan
, p. 8686 - 8688 (2013/09/23)
An enantiopure zinc complex supported by an aminophenolate ligand with multiple stereogenic centers has been diastereoselectively synthesized via the variation of the ortho-substituent of a phenoxy moiety and the N-alkyl group of a chiral pyrrolidinyl ring in the ligand framework, which displays high isoselectivity in the polymerization of rac-lactide.
