Nickel-catalysed chelation-assisted reductive defluorinative sulfenylation of trifluoropropionic acid derivatives

Abstract

Nickel-catalysed chelation-assisted reductive cross-coupling of trifluoropropanamides/esters with disulfides to afford thioacrylamides/esters with high E selectivity, involving triple C–F bond cleavage.

Transition-Metal-Free Hydrodefluoroamination of Trifluoromethyl Enones for the Synthesis of α-Fluoroenamides

“… a Reaction conditions: 1a (0.3 mmol), 2a (0.45 mmol), PhSiH 3 (0.45 mmol), and Cs 2 CO 3 (0.75 mmol) in THF (3.5 mL) at 50 °C under N 2 for 12 h. b Isolated yield. c Ratio of Z / E isomers. d Yields were determined byF NMR analysis with 4-fluoroanisole (0.1 mmol) as an internal standard. e At 70 °C. …”

“…The alkyl substituent at the C–C double bond of intermediate C reduces the electrophilicity of the β-position relative to the trifluoromethyl group and increases its steric hindrance. Consequently, the resulting ge m -difluoroalkene C becomes less prone to being attacked by N -nucleophiles , and Si -sources, , and readily undergoes an intermolecular nucleophilic vinylic substitution with N -anion species E , yielding α-fluoroenamide 3 after the displacement of the second C­(sp 3 )-F bond . In conformational mode H , steric repulsion between the hydroxyl group-containing alkyl group [R 2 CH­(OH)­CH 2 ] and the N -moiety is minimized, favoring the stereospecific formation of ( E )- 3 as the major product.…”