Mechanism of Stereochemical Control

J. A. Ewen, Mechanisms of Stereochemical Control in Propylene Polymerizations with Soluble Group 4B Metallocene/Methylalumoxane Catalysts, J. Am. Chem. Soc. 106, 6355-6364 (1984). 

The most interesting observation relative to the mechanism of stereochemical control is that the level of asymmetric induction is not linear with the enantiomeric excess of the proline catalyst.From these observations it can be concluded that (at least) two molecules of proline are involved at the stage where... 

Mechanisms of Stereochemical Control in Natural Product Biosynthesis 77... 

Table 15-5. Mechanism of stereochemical control using benzene kinetic parameters of yeast a-keto ester reductases (YKERs)100,, 10.

Ewen JA (1984) Mechanisms of stereochemical control in propylene polymerizations with soluble group 4B metallocene/methylalumoxane catalysts. J Am Chem Soc 106 6355... 

In this contribution we present the crystal structure of iPr[CpFlu]Zr(CH2>2> bulk and slurry propylene polymerization results with MAO as a cocatalyst, polymer C-13 NHR data, and kinetic or statistical models that relate the spp polymer microstructures to the structure of the metallocene and generally accepted mechanisms of stereochemical control and polymerization. 

These considerations concerning the mechanism of stereochemical control in ionic polymerization reactions, therefore, can account for the tacticities obtained in most homogeneous anionic and cationic polymerizations as shown in Tables 3 and 6, respectively (3). 

Nakamura K, Kawai Y, Miyai T, Honda S, Nakajrma N, Ohno A. Stereochemical control in microbial reduction. 18. Mechanism of stereochemical control in the diasteieoselective reduction with baker s yeast. Bull. Chem. Soc. Jpn. 1991 64 1467-1470. 

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