Chiral auxiliary control of tacticity in free radical polymerization
作者:Ned A. Porter、Timothy R. Allen、Robert A. Breyer
DOI:10.1021/ja00046a011
日期:1992.9
Chiral oxazolidine acrylamides undergo stereocontrolled free radicalpolymerization. Remarkably high degrees of tacticity have been demonstrated in the polymerization of acrylamides with these chiral auxiliaries that are derived from valine, phenylglycine, and tert-leucine. The polyacrylamides formed in these polymerizations can be converted to poly(acrylic acid), P(AA), and poly(methyl acrylate),
New chiral auxiliaries based on conformation control, a C2-symmetric 2,2-dimethylimidazolidine and 4-chiral, 2,2-dialkyloxazolidines. Synthesis and conformational analysis of acrylamide derivatives
作者:Shuji Kanemasa、Kenjiro Onimura
DOI:10.1016/s0040-4020(01)89439-4
日期:——
New chirality-controlling auxiliaries, a C2-symmetric 2,2-dimethylimidazolidine and 4-chiral 2,2-dialkyloxazolidines, are readily prepared from a C2-SYMMetriC 1,2-ethanediamine and naturally occurring alpha-amino acids, respectively. Conformational analysis of their N-acryloyl derivatives has been carried out on the basis of dynamic H-1 NMR spectroscopy and molecular mechanics calculations using MM2 program. Proper choice of the substituents at 2-, 4-, and 5-positions, in the oxazolidine cases, leads to the most effective chiral shielding of a diastereotopic acryloyl face.
Control of stereochemistry in free radical reactions with oxazolidine auxiliaries
作者:Ned A. Porter、John D. Bruhnke、Wen Xue Wu、Ian J. Rosenstein、Robert A. Breyer
DOI:10.1021/ja00020a066
日期:1991.9
Highly lk-selective asymmetric nitrile oxide cycloadditions to a C2-symmetric 1,3-diacryloyl-2,2-dimethylimidazolidine and 4-chiral 3-acryloyl-2,2-dialkyloxazolidines
作者:Shuji Kanemasa、Kenjiro Onimura
DOI:10.1016/s0040-4020(01)89440-0
日期:——
1,3-Dipolar cycloadditions of benzonitrile oxide to the acrylamides derived from a C2-symmetric 2,2-dimethylimidazolidine and 4-chiral 2,2-dialkyloxazolidines show high lk-diastereoselectivities. Easy separation of the major lk-isomers from the minor ul-diastereomers is followed by reductive removal of the chiral auxiliaries to produce optically pure 2-isoxazoline-5-methanols. Absolute diastereoselectivities were recorded in the nitrile oxide cycloadditions of 3-acryloyl-2,2-dialkyl-4-(diphenylmethyl)oxazolidines at 0-degrees-C.