Copper- and Rhodium-Catalyzed Cascade Reactions in Organic Synthesis

5 COPPER- AND RHODIUM-CATALYZED CASCADE REACTIONS IN ORGANIC SYNTHESIS 

The transition metal-catalyzed decomposition of a-cabonyl diazo compounds is a very important synthetic method, as has been reviewed [98]. Cu and Rh catalytic systems have been proved very effective for this process. From the perspective of synthetic and process chemists, such metal carbenes can undergo three major types of reactions cyclopropanation with alkenes, addition to an unsaturated C—C bond, and the formation of ylide, which have been the source of fruitful cascades. 

Enamines as Lewis bases are able to coordinate to an unsaturated transition metal which prevents the transition metal from catalyzing diazo decomposition. Among transition metals, copper has relatively low activity and can coexist with the enamine 

SCHEME 7.47 Cascade or stepwise reaction of cyclopropanation/ring-opening/iminium cyclization reaction. 

The tetrahydro-9a,4a-iminoethano-9/f-carbazole skeleton is a highly congested polycyclic ring system. It is the core structure of the indoline alkaloid akuammiline 

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Copper- and rhodium-catalyzed cascade reactions in organic synthesis... 

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