Reactions of activated aryl sydnones with electrophiles

Abstract

Electrophilic substitution on the aryl or sydnone ring of some ortho‐substituted activated N‐aryl‐sydnones is reported.

Oxadiazoles

“…Thus, 3-(2-aminophenyl) sydnone is brominated in the benzene ring para to the amino group [85] while the nitration of 3,4-diphenylsydnone affords the 4-nitrophenyl derivative. As further examples, the sydnone ring is brominated in preference to a pyrazolyl system at C3, while nitration of 3-methyl-4-phenyl sydnone affords the 4-nitrophenyl substituted derivative.…”

Coordination complexes involving sydnones as ligands

“…However, reaction in ethanol with a short reflux furnished the heteroleptic mercury complex 3 while a longer reaction provided the homoleptic 4 (Scheme 2, top). This strategy was latter used to effect the iodination of N-(2-aminophenyl) sydnone after a mercuration step, 17 or to perform cross couplings, using palladium chloride and cuprous chloride, and obtain dimers or cyclodimers like compound 5 (Scheme 2, bottom). 18 In 1988, 4-copper-3-phenylsydnone 7 was generated in situ from deprotonation of the parent sydnone 6 with butyl lithium, followed by transmetallation with copper(I) bromide.…”

“…More recently, the Taran group developed the synthesis of palladium complexes featuring either phosphines (17) or substituted bipyridines (18) as ancillary ligands in a view to produce readily 3-fluorosydnones (Scheme 6). 24 Interestingly, solely bipyridine-containing complexes reacted with Selecfluor to furnish the desired 3-fluorosydnone.…”