ChemInform Abstract: RK. VON PYRIDINIUMSALZEN 4. MITT. SYNTH. VON GAMMA‐AMINO‐PYRIDINEN

Abstract

Das Phenoxypyridin (I) reagiert mit den Hydrohalogeniden der Amine (II) (gleiche Ergebnisse erzielt man bei der Reaktion von (I)‐Hydrobromid mit den freien Aminen) bei 150‐2l0°C zu den Aminopyridinen (III) (Ausbeute 1 l bis 99%).

Synthetic applications of N-N linked heterocycles. Part 15. A facile synthesis of 4-pyridyl(aryl)amines via the reaction between 4-chloro-1-pyridiniopyridinium salts and aryl amines

“…Crude pyridone salts (1) and (2) (as chloride hydrochlorides; prepared as described previously 3 , were carefully neutralised to pH 5 to 6 with aqueous NaHC03, and then recrystallised and dried before conversion into the 4-chloro-1 -pyridiniopyridinium salts (7) and (8) with POC13. This modified procedure gave consistently higher yields of the salts (7) and (8) than that reported previous1y.J Iminiurn Salts (9) and (lo).-Generally, when equimolar amounts of a chloropyridinium salt [(7) or (8); Y = BF4] and a substituted aniline were heated together under reflux in absolute ethanol for 5 min (Method A), the intermediate iminium salt (9) or (10) was precipitated in high yield on cooling.? In certain cases, however, especially with more basic t The chlorides [(7) or (8) Y = Cl], in contrast, were very hygroscopic and gave unsatisfactory results.…”

“…Yields of iminium salts ( 9) and (lo), and of 4-pyridyl(aryl)amines ( 11) and (12), and methods of preparation Based on chloropyridiniopyridinium salts (7) or (8). Based on iminium salts (9) or (10). Products were identified from spectroscopic data, but were not isolated pure.…”

“…No 4pyridyl sulphones were observed. (9) and (10).-With few exceptions,? iminium salts were formed from arylamines rapidly, and in excellent yields.…”

“…In this respect the behaviour of the iminium salts ( 9) with cyanide ion is consistent with that of the pyridone salt However, the methyl groups in the pyridone salt (2) sterically shield the pyridinium a-positions, directing cyanide ion and other nucleophiles l2 regiospecifically to the y-position. The failure to observe 4cyanopyridine from the salts (10) is thus surprising. The extra positive charge on the salts (lo), as compared with the pyridone (2), could result both in a lengthening of the N-N bond with concomitant reduction in steric shielding by the methyl groups, and in higher charge density at the pyridinium apositions.…”

“…Yields varied between 72-85% based on the recrystallised pyridone chloride. The products were sufficiently pure for conversion into iminium salts (9) and (10). (9) and (lo).-Method A.…”