Azaphospha-Dewar-benzene

The mass spectra of phosphorus-containing heterocycles has frequently been applied for characterization and identification. Parent ions are frequently intense. Fragmentation patterns occasionally give a clue to the reactions taking place in the gas phase. 2,4,6-Triaryl-l,3-azaphosphinines show fragment ions as indicated in Figure 4, which are simply explained on the basis of cycloreversion reactions of the intermediate 3-aza-l-phosphabicyclo[2.2.0]hexadienes (azaphospha-Dewar benzenes). 

The first azaphosphaprismanes and -benzvalenes were also prepared by the above-mentioned route. The combination tri-tert-butylazete (25)/tert-butylphosphaacetylene (9 a) is initially responsible for the formation of the azaphospha-Dewar-benzene 26 (Scheme 6-6) again the reacting centers are determined by the steric demands of the two reaction partners [39]. 

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