1,3-Dipolar cycloaddition of azomethine ylides derived from imines and difluorocarbene to alkynes: a new active Pb-mediated approach to 2-fluoropyrrole derivatives

1,3-Dipolar Cycloaddition Reactions of Azomethine Ylides with Carbonyl Dipolarophiles Yielding Oxazolidine Derivatives

“…In contrast, the corresponding alkynyl esters and alkynyl ketones resulted in selective addition to the alkyne triple bond. A later study of addition of the ylides formed by imines and difluorocarbene with alkynes revealed side reactions involving addition to alkynyl aldehydes [142]. The ylide 233, formed from N-phenylbenzaldehyde imine (232) and difluorocarbene, reacted with alkynyl aldehyde 2ac to form the cycloadduct 234.…”

Reaction of Fluoro(phenyl)carbene with Schiff Bases: Synthesis of 2-Fluoro-2-phenylaziridines

“…Therefore, we made an attempt to develop a milder procedure for generation of fluoro(phenyl)carbene by analogy with generation of difluorocarbene via reduction of dibromodifluoromethane with lead or zinc in the presence of tetrabutylammonium bromide [24]. For example, the reaction of dibromodifluoromethane with activated lead in the presence of Schiff bases was successfully applied to generate geminal difluoroazomethine ylides [15]. Correspondingly, fluoro(phenyl)-carbene could be generated by reduction with metals of a,a-dibromo-a-fluorotoluene (X).…”

Fluorinated Five‐Membered Nitrogen‐Containing Heterocycles

“…1,3-Dipolar addition of dipolarophiles to azomethine ylides derived by addition of difluorocarbene to imines produces substituted 2-fluoropyrroles. 61,62 The process is illustrated below with the imine derived from benzaldehyde and aniline. Using dimethyl acetylenedicarboxylate (DMAD) as the dipolarophile produces the 2-fluoropyrrole derivative 73 (Fig.…”