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Prevention of Undesirable Isomerization during Olefin Metathesis



For the introduction of chirality into prochiral allylic alcohols we used a titanium alkoxide tartrate epoxidation (DIPT???) catalyst which is highly effective. It was found that increasing the size of the alkyl group in the tartrate ester significantly increases the rate difference for epoxidation of the S and R enantiomers. The enantiomeric excess realized in an asymmetric synthesis is simply a consequence of the energy difference between two diastereomeric transition states the only way to improve the % ee is to increase that energy difference The energy difference represents a constant and unrelenting differential pressure upon the two enantiomers. (trivial);. So we continued this winnowing until the last molecule of the more reactive enantiomer is swept away, and one is left with a substance possessed of absolute enantiometric purity. This is quite usual approach. Instead, say which R allows to obtain highest ee.


Graphical abstract: give ee intervals, simplify


Prevention of Undesirable Isomerization during Olefin Metathesis



Olefin isomerization is example of unwanted reactions in olefin metathesis with unknown mechanism (what mechanism? Metathesis?). Self-metathesis and isomerization of (Z)-5-tert-butyldimethyl-silyloxy-2-pentenoate served as an excellent system for initially studying the effects of additives on the isomerization process. According to experiment acid-type compound work well in preventing olefin migration during olefin metathesis reactions. Which additive works the best? Give RECOMMENDATION

Graphical Abstract 40oC - correct, Why CD2Cl2? what is 2?, what is additive specify. Use simpler or more generalized structures..

Date: 2014-12-22; view: 1045

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