The First Example of Photogeneration of a Pyrrole Molecule on the Basis of 6π-Electrocyclization of 2-Arylbenzofurans Containing a Pyrazole Fragment.

The photochemical behavior of terarylenes containing benzofuran and aminopyrazole fragments was studied. It was found that the presence of an amino group in the structure of the studied terarylenes blocks photocyclization. At the same time, the transformation of the amino group into a pyrrole fragment allows one to remove the aforementioned blocking effect. As a result, UV-irradiation of pyrrole-containing compounds leads to 6π-electrocyclization of the 1,3,5-hexatriene system with the formation of polycyclic molecules. For the first time an efficient method for the photogeneration of pyrrole molecule using the phototransformation of substituted 2-arylbenzofurans was proposed. The structure of one of the target products was established by X-ray diffraction. [ABSTRACT FROM AUTHOR]