Direct synthesis of N-phosphanyl-heterocyclic carbenes

A Strategy to Control the Reactivation of Frustrated Lewis Pairs from Shelf‐Stable Carbene Borane Complexes

“…The synthesis of the carbene precursors, PoxIm⋅HOTf ( 1 a – 1 c ), followed a pathway that was previously developed by Kostyuk et al[12] and Hofmann et al[13] to prepare N-phosphanyl-substituted imidazolium salts. Without isolation of these air-sensitive imidazolium species, oxidation of the N -phosphanyl group with aqueous H 2 O 2 gave 1 a – 1 c , which were isolated as bench-stable solids.…”

Synthesis and properties of heteroaromatic carbenes of the imidazole and triazole series and their fused analogues

“…Similar compounds were isolated by direct phosphanylation of lithium benzimidazoles with di-tert-butylphosphanyl chloride according to Scheme 10 or by deprotonation of the appropriate N-phosphanylbenzimidazolium salts with NaHMDS, Me2NLi or MeLi. 65,110 Scheme 22. N-phosphanylbenzimidazol-2-ylidenes and synthesis of N-ferrocenylbenzimidazolium salts.…”

“…65,110 As a consequence, it was demonstrated that the intermediates in the electrophilic substitution reactions of azoles are carbenic in nature. Previously, cyclic ylide structures had been assigned to such intermediates on the basis of the resonance possible for these carbenes.…”

“…297 The reaction of phosphanylated imidazoles and 1,2,4-triazol-5-ylidenes 62C to phosphanylazoles 62D proceeds similarly. 65,200,201 Thus, although in mainstream heterocyclic chemistry the N-substituent migration involves a carbene carbon atom, shifts to the 4 and 5 positions of the imidazol-2-ylidene nucleus are also possible.…”

Investigation of N‐ and C‐Phosphanylation of [1,2,4]Triazolo[4,3‐a]pyridines

“…The third approach is to treat lithium derivatives of heterocycles, containing a pyridine-type nitrogen, with phosphanylhalides (Scheme 3) [4,5,13,14]. Lithiation of heterocyclic compounds is somewhat similar to phosphanylation.…”