Gold(I)‐Catalyzed Aminohalogenation of Fluorinated N′‐Aryl‐N‐Propargyl Amidines for the Synthesis of Imidazole Derivatives under Mild Conditions

A procedure for the synthesis of fluorinated imidazole derivatives from propargyl amidines has been developed. Under gold(I) catalysis, propargyl amidines were converted into 5‐fluoromethyl imidazoles in the presence of Selectfluor through a cascade cyclization/fluorination process. In contrast, imidazole‐5‐carbaldehydes were obtained in high yields when N‐iodosuccinimide (NIS) was used as the halogenating reagent. The polarity of the solvent and light had significant impact on the formation of the carbaldehydes. These transformations showed excellent functional‐group tolerance. An unfluorinated substrate with an electron‐withdrawing group also underwent aminohalogenation to give the corresponding product in good yield. Mechanistic investigation revealed the general pathways of these transformations.     

Catalytic enantioselective alkene aminohalogenation/cyclization involving atom transfer

Problem solved: the title reaction was used for the synthesis of chiral 2-bromo, chloro, and iodomethyl indolines and 2-iodomethyl pyrrolidines. Stereocenter formation is believed to occur by enantioselective cis?aminocupration and C-X bond formation is believed to occur by atom transfer. The ultility of the products as versatile synthetic intermediates was demonstrated, as was a radical cascade cyclization sequence.