Enantioconvergent 6π Electrocyclization Enabled by Photoredox Racemization

Visible light-induced reductive aza-6π electrocyclization access to phenanthridines

“…S1†). By combining the reported aza-6π electrocyclization concept 13 and the experimental results, we proposed a plausible reaction pathway (Scheme 3). The initial step starts from the reduction of the nitro group in nitroaromatics by B 2 nep 2 , generating aminoaromatics I .…”

HFIP-Promoted Divergent Cycloadditions of Difluoroenoxysilanes with 2-Indolylmethanols: Synthesis of Fluoro 2H-Pyrano[3,4-b]indoles and gem-Difluoro Cyclopenta[b]indoles

“…Interestingly, when difluoroenoxysilanes are used as nucleophilic reagents to react with diaryl 2-indolylmethanols, the “umpolung” C3-electrophilic cycloaddition does not furnish the desired [3+2] cyclized product (Scheme d). Instead, an unexpected oxa-6π-electrocyclization occurs, in which the dehydrofluorination process turns out to be a critical parameter (Scheme e). On the contrary, the reaction with dialkyl 2-indolylmethanols undergoes a rarely reported C3-nucleophilic [3+2] cycloaddition (Scheme f).…”