320778-99-2Relevant academic research and scientific papers
Mechanism of living lactide polymerization by dinuclear indium catalysts and its impact on isoselectivity
Yu, Insun,Acosta-Ramirez, Alberto,Mehrkhodavandi, Parisa
experimental part, p. 12758 - 12773 (2012/09/05)
A family of racemic and enantiopure indium complexes 1-11 bearing bulky chiral diaminoaryloxy ligands, H(NNOR), were synthesized and fully characterized. Investigation of both the mono- and the bis-alkoxy-bridged complexes [(NNOR)InX]2[μ-Y][μ-OEt] (5, R = tBu, X = Y = Cl; 8, R = Me, X = I, Y = OEt) by variable temperature, 2D NOESY, and PGSE NMR spectroscopy confirmed dinuclear structures in solution analogous to those obtained by single-crystal X-ray crystallography. The dinuclear complexes in the family were highly active catalysts for the ring-opening polymerization (ROP) of lactide (LA) to form poly(lactic acid) (PLA) at room temperature. In particular, complex 5 showed living polymerization behavior over a large molecular weight range. A detailed investigation of catalyst stereoselectivity showed that, although (R,R/R,R)-5 is highly selective for l-LA, only atactic PLA is obtained in the polymerization of racemic LA. No such selectivity was observed for complex 8. Importantly, the selectivities obtained for the ROP of racemic LA with (R,R/R,R)-5 and (R,R/R,R)-8 are different and, along with kinetics investigations, suggest a dinuclear propagating species for these complexes.
An efficient method for the preparation of N,N-disubstituted 1,2-diamines
Mitchell,Finney
, p. 8431 - 8434 (2007/10/03)
C2-Symmetric 1,2-diamines are useful precursors to numerous reagents used in asymmetric synthesis and catalysis. We report here an efficient protocol for converting the two most commonly used trans-1,2-diamines to N,N-disubstituted derivatives, a transformation that simplifies the preparation of non-C2-symmetric diamines. Central to the method is the high-yielding conversion of the diamines to the corresponding monoacetylated derivatives via imidazoline intermediates. (C) 2000 Published by Elsevier Science Ltd.
