Diastereoselective synthesis of chiral aminophenolate magnesium complexes and their application in the stereoselective polymerization of rac-lactide and rac-β-butyrolactone. Issue 27 (15th June 2016)

• Record Type: Journal Article
• Authors: Wang, Haobing; Guo, Jianshuang; Yang, Yang; Ma, Haiyan
• Is Part Of: Dalton transactions. Volume 45:Issue 27(2016)
• Page Start: 10942
• Page End: 10953
• Publication Date: 2016-06-15
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt01126h
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : 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. Abstract : 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 aminophenolsL 1–10 H [L = ( S )-{[(1-R 4, 2-pyrrolidinyl)CH2 N(R 3 )-]}CH2 -(6-R 1 -4-R 2 )-C6 H2 O − ] in a 1 : 1 molar ratio in toluene gave the chiral aminophenolate magnesium silylamido complexes L 1–10 MgN(SiMe3 )2 as enantiopure compounds or as pairs of diastereomers. As determined by X-ray analysis, structuresa andb of diastereomer mixtures adopt the configuration of S C S N R N R Mg -a and S C S N S N S Mg -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 ( P m = 0.67) to heteroselective-enriched ( P r = 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, complexes3–9 can efficiently initiate the ring-opening polymerization of rac -BBL in a controlled manner, giving moderate syndiotactic ( P s up to 0.73) PHBs.