N-Azinylpyridinium N-Aminides:  Intermediates for the Regioselective Synthesis of 3-Fluoro-2-aminopyridine Derivatives

(Me3Si)3SiH: Twenty Years After Its Discovery as a Radical‐Based Reducing Agent

“…can be achieved either by replacement of a pyridinium moiety with hydrogen (Scheme 2) [19] or by reduction of nitroxides. [20] A C H T U N G T R E N N U N G (Me 3 Si) 3 SiH is useful for the reduction of phosphine sulfides and phosphine selenides under free radical conditions to give the corresponding phosphines or, after treatment with BH 3 ·THF, the corresponding phosphine-borane complex in good to excellent yields.…”

Pyridinium N-(2′-Azinyl)Aminides: Regioselective Synthesis of 2-Alkylaminoazines

“…More recently, methods employing palladium catalyzed crosscoupling reactions or amination of cuprates with N-alkylhydroxylamines were reported in the syntheses of N-alkylheteroarylamines. 17,18 Going back to a classical approach, we planned to use a permanent nitride species, such as the pyridinium N-(2 Hazinyl)aminides 4-6 (Scheme 2), [19][20][21][22] where the exocyclic nitrogen anion is stabilized by the presence of a pyridinium moiety. Moreover, the a-nuclear nitrogen, at least in pyridine derivatives, is partially blocked by an intramolecular hydrogen bond, making the alkylation regioselective.…”

Pyridinium-N-(2-pyridyl)aminides and related compounds: a theoretical study

“…[1][2][3][4][5][6][7][8][9][10] These compounds belong to the class of conjugated heterocyclic Nylides. [11][12][13][14][15][16] Heterocyclic mesomeric betaines have been the subject of extensive investigation, mainly because of their 1,3-dipolar character, which allows them to take part in 1,3-dipolar cycloadditions with various dipolarophiles, thus generating novel five-membered aza heterocycles.…”

“…Amongst the rich reactivity of these compounds, Alvarez-Builla and coworkers discovered that that of azinium-N-ylides is controlled by the intramolecular hydrogenbond (HB) shown in Figure 1. 1,3,5,6 For instance, alkylation occurs exclusively on the exocyclic nitrogen atom (the N -). However, when a radical is formed, the reactivity is modified and this was attributed to a new HB between the C · and the pyridinium C-H involving a conformational change.…”