ABSTRACT
Herein, we describe the synthesis of 5-fluoro-dihydroindolizines via dual C-F bond cleavage in a trifluoromethyl group. The photocatalytic defluorinative coupling of pyrrole-2-acetic acids and α-trifluoromethyl alkenes cleaved the first C-F bond, providing gem-difluoroalkenes bearing an unprotected pyrrole motif. Subsequently, an intramolecular SNV reaction closed the ring by forming a C-N bond concomitantly with the cleavage of the second C-F bond. Using indole-2-acetic acids as the substrates, the reactions also allow the assembly of 6-fluoro-dihydropyrido[1,2-a]indoles.
Subject(s)
Alkenes , Pyrroles , Acetates , Hydrocarbons, Fluorinated , Indoles/chemistryABSTRACT
gem-Difluoroalkene bearing a carbonyl group is a challenging target to synthesize by conventional methods. Herein we report a mild and concise route to access the target compounds through the visible-light-mediated direct ß-C-H gem-difluoroallylation of aliphatic aldehydes and cyclic ketones. Upon a synergistic combination of photoredox catalysis and organocatalysis, various α-CF3 alkenes were employed as the gem-difluoroallylation reagents via the C-F bond cleavage.
ABSTRACT
A visible-light-promoted redox neutral γ,γ-difluoroallylation of cycloketone oxime ethers with trifluoromethyl alkenes through C-C and C-F bond cleavage has been achieved, which affords various cyano-substituted gem-difluoroalkenes in generally good yields. The reaction provides a facile protocol for forming gem-difluoroalkene functionality and a cyano group while incorporating them into one molecule. The conversion of the resulting cyano-substituted gem-difluoroalkenes to cyclic monofluoroalkenes via a second C-F bond cleavage was also described.
