Doubly confused porphyrins

The unnatural porphyrin family still fascinates the imagination. This year, to give a flavor for the diversity, there has appeared hybrid calixphyrins <00OL3103>, doubly A-confused porphyrins , unsymmetrical porphyrins attached to a modified 5,10,15,20-tetra (4-(2-trimethylsilylethynyl)phenyl]-21-23-dithiaporphyrin <00TL3709>,... 

In spite of its unusual structural outcome, the N-fusion reaction is a very general process. It was observed in a number of other N-confused macrocycles. For instance, an N-fused intermediate forms in the synthesis of trans doubly N-confused porphyrin 96 [238], N-fusion was also induced by the reaction with PhBCl2, in which case the reaction was promoted by the small radius of the coordinating boron(III) center [251], The resulting boron complexes were also aromatic, even though in some cases further chemical modification of the macrocycle took place (as in 110). The fusion process, which appears to be a nucleophilic addition-elimination, is reversible, and N-fused macrocycles can often be reopened when treated with nucleophiles such as alkoxides [248, 249],... 

To mention a few more, -substituted porphycene (37), a structural isomer of porphyrin, is synthesized by the method developed by Vogel and coworkers through a McMurry coupling of bipyrrole dialdehydes (Scheme 9.4) [35]. Doubly N-confused porphyrin, such as 38, can be efficiently synthesized by a method proposed by Furuta and coworkers (Scheme 9.5) [36]. 

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