Synthesis of Alkyl Substituted Carbatripyrrins and Their Application to the Preparation of Carbaporphyrins and Oxacarbaporphyrins

Unsubstituted carbatripyrrins have previously been shown to be useful intermediates in the synthesis of benzocarbaporphyrins and related core-modified analogues. However, the absence of substituents often resulted in the formation of poorly soluble products. In this study, four examples alkyl substituted carbatripyrrins were constructed by base-catalyzed condensation of dihydrofulvenes with pyrrole aldehydes. Further reaction with a pyrrole dialdehyde in the presence of trifluoroacetic acid afforded a series of carbaporphyrins, while reactions with 2,5-furandicarboxaldehyde generated oxacarbaporphyrins. These results demonstrate that alkyl substituted carbatripyrrins are promising precursors to new carbaporphyrinoid structures.