The Chemistry of N-Substituted Pyridinium Salts

Syntheses, physicochemical and b i o l o g i c a l p m p e r t i e e of B-substituted pyridinium salts, as well a s t h e i r applications a r e deecribed. I. INTBOIFJCTIONThe present paper, a continuation of our research ooncerning cycloaddition reactions of benso[h]naphthyridinesl-7 deals with N-substituted pyridinium salts and t h e i r analoguee; N -a m i n o p y r i d i n i ~, precursors of N-iminoylides, used i n cycloaddition reac-8-1 3 t i o n s a r e not described here .Pyridinium salts, i n t e r e s t i n g f o r t h e i r r e a c t i v i t y , b i o l o g i c a l p r o p e r t i e s and appuoau o n s , compounds o f g r e a t importance.Among r e a c t i o n s of pyridinium salts one ought t o mention t h e i r nucleophilic substitut i o n with m i n e s ; numerous publications deal w i t h k i n e t i c measurements and meohanism e l u c i d a t i o n of these r e a c t i o n s , along with t h e study of p y r i d i n e ring-substituents' influence on its e f f e c t i v e n e s s a s t h e leaving, group14-16.Pyridinium salts are synthons of pyridinium N-methylides used i n d i p o l a r cycloaddition reaction^'^-^^.A s t h e material concerning t h e r e a c t i v i t y of pyridinium s a l t s i s very large20-35, this topic i s not included here.I n t h e present work t h e syntheees of pyridinium s a l t s and t h e i r physicochemical prop e r t i e s , along with t h e i r a p p l i c a t i o n s a r e presented. SYNTHESLSSynthetic approaches f o r pyridinium salts, described i n r e c e n t publiaations aan be divided i n t o :A. Quaternieation r e a c t i o n s of pyridines w i t h organic halides, and r e l a t e d reactions. B.Reactions of pyrylium salts with primary amines.C. Other synthesea.A. QUATHUIIZBTIC4 REACTIONS OF PYRIDINLS WITH ORGANIC HALIDES, AND RELATED REACTIONS N-Vinylpyridinium salts, i n t e r e s t i n g as polymer colnponents can be obtained by two 3 6 , 3 1 procedures. ref luxI n the study of vinylpyridinium salts, t h e i r d e r i v a t i v e s 1 have been prepared i n t h e r e a c t i o n proceeding via an addition-elimination mechanism 38: So f a r , few N-t-akylpyridinium salts a r e known; examples of them a r e 2, obtained 39 from pyridine and corresponding a l k y l bromide in t h e presence of s i l v e r perchlorate .