Diphosphinocarbenes , cyclic

Analogs of NHCs such as cyclic diphosphinocarbenes [81] or alkyl-monoamino-carbenes (CAACs) [82, 83] were then designed. As compared to NHCs, their... 

Analogs of NHCs such as cyclic diphosphinocarbenes [81] or alkyl-monoamino-... 

Bertrand and coworkers have reviewed the topic of stable carbenes based on scaffolds other than diaminocarbenes [47]. Diphosphinocarbenes, aminophosphi-nocarbenes, cyclic (alkyl)amino carbenes, cyclic (amino)ylidic carbenes, cycloprope-nylidenes, cyclic bent allenes, carbodiphosphoranes, and vinylidenephosphoranes have all been reported (examples 37-44, respectively, in Figure 1.24a). Use of the [RhCl(CO)2(L)j system for measuring TEPs allows the electron-donating ability of these systems to be ranked and compared to those of NHCs and abnormally bound NHCs (Figure 1.24b). 

An unprecedented thermal ring contraction has been reported in the formation of the four-membered azaphosphete (100) from the five-membered cyclic carbodiphos-phorane (101). The reaction is believed to take place by the interconversion between (101) and the acyclic diphosphinocarbene (102) and benzonitrile. ... 

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