Nucleophilic Carbenes: An Incredible Renaissance

摘要

Carbenes 1 can be considered typical representatives of reactive intermediates and have found a broad range of applications in synthetic chemistry. Their impressive reactivity is comprehensively documented in two thick volumes of a standard referenceseries on organic synthesis. As a result of the deficit of electrons they have electrophilic character, provided that the two subsfituents R are not electron donors. If this is not the case as. for example in the system 3A <--> 3B, the donor groups enforce nucleophilic character at the carbene center. The ambiphilic carbenes 2 having both a donor and an acceptor substituent occupy a position between carbenes 1 and 3. Only carbenes of type 3 can be isolated as stable compounds ("carbenes in a bottle"), and these were realized for the first time just a few vears ago.