Fluorinated cyclopropanes for 2-heterosubstituted electron-rich indolizine synthesis
Angelina Yu Bobrova1, Maxim A Novikov1, Julia V Burykina1
1N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky prosp., 119991 Moscow, Russia. bbrv@ioc.ac.ru.
Abstract:
Fluorinated cyclopropanes were proven to be valuable precursors for a wide range of 2-heterosubstituted electron-rich indolizines, hardly accessible by other methods due to their instability. Copper(I) activation of C-X bonds permits disubstituted fluorocyclopropanes to undergo ring opening in the presence of pyridines, yielding (2-fluoroallyl)pyridinium salts. These intermediates were found to undergo base-promoted cyclization, either retaining the fluorine atom or undergoing intermolecular fluorine substitution with additional NuH, producing two- or three-component-derived 2-F,N,S,O-subtituted indolizines. This strategy allows 2-heterosubsituted indolizines with different 1,3-substitutition and nucleophilic parts to be prepared, including ones with functional groups capable of coupling with biologically relevant structures. The 2-heteroindolizines obtained exhibit blue-light emission with high intensity in DMSO, good Stokes shift and notable quantum yields.
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