الفهرس 
Stereoselective cyclopropanation reactionsOnly 14 pages are availabe for public view
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Abstract
1.1. Aim of the work
New asymmetric methods to generate the cyclopropane motif have attracted
widespread attention from the synthetic community owing to their ubiquitous
presence in a diverse range of natural products and their crucial role in the mode of
action of many therapeutic agents.
Furthermore, the rigid structure and strain-driven reactivity make them attractive
intermediates in the synthesis of complex molecules. Because of these important
properties and the need for efficient methods for their stereoselective formation, the
synthesis of cyclopropane containing molecules has become a platform for the
development of new asymmetric catalytic processes. In the last few years numerous
metal-catalyzed and organocatalytic intermolecular cyclopropanation reactions have
been reported that enable the generation of discrete three-membered ring systems
with high diastereoselectivity. The cyclopropane ring is a constituent in more than
4000 isolated natural products and 100 biologically active agents.
Thus the present work examines primarily the utility of organic catalysts such as (S)-
proline (256), (S)-prolinol (257), (S)-(2)-(diphenyltrimethylsiloxymethyl)-pyrrolidine
(258) and (S)-(2)-(diphenyltrimethylsiloxymethyl)-pyrrolidine.TfOH (259) in
organocatalytic cyclopropanation reactions between a-methacrolein (260) and a-
diazoacetic ester as well as a-diazophosphonates as shown below .