1,3-dipolar cycloaddition of fluorinated azomethine ylides at the C=N bond

Abstract

Azomethine ylides generated by reaction of difluorocarbene with N-alkyl-and N-arylimines derived from benzaldehyde and benzophenone react with N-benzylidenebenzenesulfonamide in a regioselective fashion, yielding the corresponding imidazolidin-4-ones via 1,3-dipolar cycloaddition at the C=N bond. Ylides generated from benzaldehyde imines give rise to mixtures of stereoisomeric 2,5-diphenyl-1-(phenylsulfonyl)imidazolidin-4-ones, the cis isomer prevailing.

Fused aziridines as sources of azomethine ylides

“…Initial cycloaddition products 39 can be converted almost quantitatively into the tricyclic derivatives 40 by refluxing with Pd/C in toluene. It is known that dipolarophiles with a C=N bond are far less active towards azomethine ylides than electron-deficient alkenes and alkynes, and this applies even to imines containing electron-withdrawing groups [19]. At the same time strained cyclic analogs of imines, 2H-azirines, are often quite effective as traps for 1,3-dipoles, including the azomethine ylides generated from fused aziridines.…”

Intramolecular Cycloaddition Azomethine Ylides and α‐(Trifluoromethyl)styrenes as Dipolarophiles

“…While several examples of intermolecular reactions have been reported in the literature, the intramolecular AMY cycloaddition reaction (AMYR) incorporating fluorine‐containing substrates remained almost unexplored. Only four examples have been described to date; two of them take advantage of the use of difluorocarbene which generates the corresponding dipole by reaction with aryl and alkyl imines of O‐acylated salicylaldehydes and then undergo the intramolecular cycloaddition . The third employs a fluorinated dipolarophile, difluorinated allylic alcohol that reacted with the AMY generated from sarcosine .…”

An Aza Cyclopropylcarbinyl-Homoallyl Radical Rearrangement–Radical Cyclization Cascade. Synthesis of Dibenzoimidazoazepine and Oxazepine Derivatives

“…Cycloadditions of iminium ylides to the CN bond are quite rare due to low dipolarophilic activity of imines . The CN bond of azirines is a more active dipolarophile toward iminium ylides; ,, nevertheless cycloadditions to the multiple bond of this strained ring are practically unexplored.…”