[4 + 2] Cycloaddition of trifluoromethyl ketimines with 2-alkenyl azaarenes through selective C–F bond cleavage of CF₃

Abstract

We have developed a new [4+2] cycloaddition of trifluoromethyl ketimines with 2-alkenyl azaarenes through selective C-F bond cleavage of CF3. The reactions are promoted by 2,2,6,6-tetramethylpiperidine (TMP) under mild conditions...

Synthesis of Pentasubstituted meta‐Fluoropyridines via [4+2] Cycloaddition and Aromatization between Trifluoromethyl Ketimines and Maleimides

“…Scherbinina reported the synthesis of pentasubstituted meta ‐fluoropyridines via photoredox‐mediated coupling of α , α ‐difluoro‐ β ‐iodoketones with silyl enol ethers (Scheme 1b) [12] . Very recently, we developed a [4+2] cyclization of trifluoromethylated ketimine and vinyl pyridine for the synthesis of cis ‐difluorotetrahydropyridines via single C−F bond cleavage [14] . Herein, we present a novel synthetic method for the synthesis of pentasubstituted meta ‐fluoropyridines by [4+2] cyclization and aromatization through double C−F bond cleavages (Scheme 1c).…”

“…[12] Very recently, we developed a [4 + 2] cyclization of trifluoromethylated ketimine and vinyl pyridine for the synthesis of cis-difluorotetrahydropyridines via single CÀ F bond cleavage. [14] Herein, we present a novel synthetic method for the synthesis of pentasubstituted meta-fluoropyridines by [4 + 2] cyclization and aromatization through double CÀ F bond cleavages (Scheme 1c). In our study, maleimide was chosen to react with trifluoromethyl ketimines under mild condition.…”

Cu catalyzed [4 + 2] cycloaddition for the synthesis of highly substituted 3-fluoropyridines

“…21 Very recently, we developed a [4 + 2] cyclization of trifluoromethylated ketimine and vinyl pyridine for the synthesis of cisdifluorotetrahydropyridines via single C-F bond cleavage. 22 Herein, we report a novel synthetic method for the synthesis of 3-fluoropyridines by [4 + 2] cyclization and aromatization through double C-F bond cleavages (Scheme 1d). At the outset of this investigation, we used benzyl trifluoromethyl ketimine 1a (0.3 mmol) and 3-acryloyloxazolidin-2-one 2a (0.1 mmol) as model substrates to test the reaction (Table 1).…”

“…21 Very recently, we developed a [4 + 2] cyclization of trifluoromethylated ketimine and vinyl pyridine for the synthesis of cis -difluorotetrahydropyridines via single C–F bond cleavage. 22 Herein, we report a novel synthetic method for the synthesis of 3-fluoropyridines by [4 + 2] cyclization and aromatization through double C–F bond cleavages (Scheme 1d).…”