Katalytische asymmetrische Halogenfunktionalisierung von Alkenen – eine kritische Betrachtung

Abstract

Obwohl die Halogenierung von Alkenen seit Jahrhunderten bekannt ist, wurden enantioselektive Varianten dieser Reaktion erst vor kurzem entwickelt. Die in den vergangenen drei Jahren beschriebenen katalytischen enantioselektiven Varianten von Halogenfunktionalisierungen mit den vier gängigen Halogenen sind wichtige Durchbrüche, stellen aber erst die Anfänge eines im Entstehen begriffenen Gebiets dar. Dieser Kurzaufsatz bietet eine kritische Betrachtung der Herausforderungen, die mit der Entwicklung allgemein anwendbarer und hoch enantioselektiver Halogenfunktionalisierungen einhergehen. Zudem liegt der Schwerpunkt hier anders als bei früheren Übersichten zu diesem Gebiet darauf, die verschiedenen Katalysearten und Strategien zur asymmetrischen Induktion aufzuzeigen.

Catalytic, Enantioselective, and Highly Chemoselective Bromocyclization of Olefinic Dicarbonyl Compounds

“…Notably, alkyl-substituted substrates gave products with good ee values in most cases (Table 3, entries 7-16). [1,11] Moreover, this catalytic protocol was compatible with various protecting groups, including OTBS, OMOM, isopropyldene, and N-Boc (see Table 3). [1,11] Moreover, this catalytic protocol was compatible with various protecting groups, including OTBS, OMOM, isopropyldene, and N-Boc (see Table 3).…”

“…[1] The resulting enantioenriched heterocycles form the core of many natural products and pharmaceutically important intermediates. [1] The resulting enantioenriched heterocycles form the core of many natural products and pharmaceutically important intermediates.…”

C3‐Symmetric Cinchonine‐Squaramide‐Catalyzed Asymmetric Chlorolactonization of Styrene‐Type Carboxylic Acids with 1,3‐Dichloro‐5,5‐dimethylhydantoin: An Efficient Method to Chiral Isochroman‐1‐ones

“…[3,4] Given its importance, asymmetric halolactonization has been actively pursued since Bartlett and co-workers described the first stereoselective iodolactonization, [5] in particular, bromolactonization and iodolactonization have become well established in recent years ( Figure 1). [6,7] The rapid development has still continued, and a number of newly structured organocatalysts such as thiocarbamate, urea, trisimidazoline etc. have been developed by several other groups.…”

Switchable Stereoselectivity in Bromoaminocyclization of Olefins: Using Brønsted Acids of Anionic Chiral Cobalt(III) Complexes

“…After the diastereoselective synthesis of sodium salts and Brønsted acids of anionic chiral cobalt(III) complexes was achieved, [8] we chose bromoaminocyclization of olefins as ab enchmark reaction, [9,10] which has received increasing interest as the corresponding products (e.g., pyrrolidines) are core structural elements in pharmaceuticals and organocatalysts, [11] and thereby are of high synthetic significance.T he reaction of the g-amino alkene 2a with N-bromosuccinimide (NBS) was initially examined in the presence of 5mol %o f the sodium salts of anionic chiral cobalt(III) complexes, L-(S,S)-1a-c ( Table 1). As anticipated, the desired reaction proceeded smoothly to give the 2-substituted pyrrolidine 3a in good yields,b ut with low levels of enantioselectivity (entries 1-3).…”