Highly Asymmetric-selective and Stereoselective Polymerization of (RS)-α-Methylbenzyl Methacrylate with Cyclohexyl-magnesium Bromide-Axially Dissymmetric 2,2′-Diamino-6,6′-dimethylbiphenyl System

Abstract

ABSTRACT:Enantiomer-selective polymerization of (RS)-IX-methylbenzyl methacrylate [(RS)-MBMA] was investigated in toluene at -30oc. Reaction products between cyclohexylmagnesium bromide (cHexMgBr) and axially dissymmetric 2,2 '-diamino-6,6' -dimethylbiphenyl (AMB) in the mole ratio of 1.5: I were used as a chiral initiating system. The polymer produced a biphenyl group from the catalyst fragment. The polymerization proceeded in an anionic coordination mechanism and the racemic monomer was kinetically resolved during the course of the reaction. The enantiomer selectivity ratio when using (R)-AMB was estimated to be r<sl= 18.0 according to the integrated composition equation for an "ideal" copolymerization of the enantiomeric monomers. Most parts of the polymer were found to be of full isotacticity from inspection of the 13 C NMR spectrum. Some physical properties of the polymer strongly suggested that it is a mixture of (R)-and (S)-homopolymers. This may be an example of an asymmetricselective (stereoelective) and stereoselective polymerization of vinyl monomer. In the copolymerizations between (RS)-MBMA and achiral methacrylates, the catalyst also showed high selectivity toward (RS)-MBMA. Each of the copolymers from methacrylates of methyl, benzyl, and diphenylmethyl alcohols was coisotactic, and the enantiomer selections were consistent with that observed for the homopolymerization. On the other hand, both the isotacticity of copolymer and the selection greatly decreased in the copolymerization with IX,IX-dimethylbenzyl methacrylate which has no hydrogen at the IX-carbon of the ester group.

Structure and Reactivity of Chelating Imido−Amido Complexes of Tantalum. Mechanistic Studies on the Addition of Silanes to Ta−N Multiple Bonds

“…The starting material for the synthesis of the target silylamine ligand, 2,2′-diamino-6,6′-dimethylbiphenyl (1), was prepared according to literature procedures. 42 N-Silylation of this diamine was achieved via deprotonation of 1 in THF followed by reaction of the resulting dianion with Me 3 SiCl (eq 1). N,N′-Bis(trimethylsilyl)-2,2′-diamino-6,6′dimethylbiphenyl (2) was obtained in 84% yield as colorless crystals from pentane.…”

Synthesis, structure, and catalytic activity of titanium(IV) and zirconium(IV) amides with chiral biphenyldiamine-based ligands

“…All organic solvents were freshly distilled from sodium benzophenone ketyl immediately prior to use. (R)-2,2 0 -Diamino-6,6 0 -dimethyl-1,1 0 -biphenyl (>98% ee) [25], (R)-2-amino-2 0 -(dimethylamino)-6,6 0 -dimethyl-1,1 0 -biphenyl [21], M(NMe 2 ) 4 [26], 2,2-dimethylpent-4-enylamine [27], 2,2 0 -dimethylhex-5-enylamine [27], and 1-(aminomethyl)-1-allylcyclohexane [28] were prepared according to literature methods. All chemicals were purchased from Aldrich Chemical Co. and Beijing Chemical Co., and used as received unless otherwise noted.…”

Synthesis and X-ray structures of rhodium complexes with new chiral biaryl-based NHC-ligands

“…(S)-2,2 0 -Diamino-6,6 0 -dimethyl-1,1 0 -biphenyl [26], (S)-2- amino-2 0 -dimethylamino-1,1 0 -binaphthyl [27][28][29][30], (R)-2-amino-2 0 -dimethylamino-6,6 0 -dimethyl-1,1 0 -biphenyl [27][28][29][30] and (R)-2-amino-2 0 -methoxy-6,6 0 -dimethyl-1,1 0 -biphenyl [31] were prepared according to literature methods. Infrared spectra were obtained from KBr pellets on an Avatar 360 Fourier transform spectrometer.…”