Photochemistry of o-pyrrolylstilbenes and formation of spiro-2H-pyrroles and their rearrangement to dihydroindoles.
Excited states of stilbenylpyrroles 1a-1c deactivate by two photochemical processes: cis-trans-isomerization and hydrogen transfer of NH to the stilbene double bond. NH-transfer results in the formation of two quinone dimethane intermediates, 10 and 11, and biradicals 12. Intramolecular cyclization of intermediates 10-12 gives rise to polycyclic compounds spiro-2H-pyrroles 7, pyrroloisoindoles 3, and pyrroloisoquinolines 8. Spiro-2H-pyrroles 7 rearrange on silica gel, giving dihydroindoles 2.
Basarić
Nikola
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Division of Organic Chemistry and Biochemistry, and NMR Center, Institute Ruder Boskovic, Bijenicka cesta 54, 10,000 Zagreb, Croatia. mbasaric@irb.hr
Marinić
Eljko
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Sindler-Kulyk
Marija
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