2.4.6- Triphenylpyridinium salt

Photocyclization of 2,4,6-triphenylpyridinium salts 64 by irradiating by 313 nm gave 7-substituted 2,4-diphenyl-6,7-dihydropyrido[2,l-u]phthalazi-nium salts 62 (94MI1). 

Thermolysis of JV-thioacylamino-2,4,6-triphenylpyridinium salts (110) leads to complete decomposition. Heating the salts with triphenylpyridine gives the nitriles (RCN) by loss of sulfur.88... 

Alkyl-2,4,6-triphenylpyridinium salts 238 transfer the iV-substituent R-CH2 onto a range of... 

Another new synthesis of isocyanates, and yet another example of the synthetic usefulness of 2,4,6-triphenylpyridinium salts, is based on the thermolysis of (58), and offers an alternative procedure to the Curtius reaction (Scheme 58). 

A further example of the use of 2,4,6-triphenylpyridinium salts in organic synthesis is the direct conversion of primary amines into azides. Thus, the pyridinium salts (33) are smoothly converted into azides (34) by reaction with sodium azide in DMF at 130 "C (Scheme 47). 

Various reducing agents produce from l-methyl-2,4,6-triphenylpyridinium salts a blue free radicaP . TRe properties of l,r-dialkyl-l,l, 4,4 -tetra-hydro-4,4 -dipyridyls have been interpreted in terms of dissociation into mononuclear free radicals, and the dissociation evidently occurs more readily with the tetrahydro-dipyridyls formed from 4-substituted pyridinium... 

Heterocyclic variations on the basic stilbene — phenanthrcne theme are provided by many systems in which one or both of the phenyl groups of stilbene is replaced by a heteroaromatic group, or in which there is a pair of phenyl groups on adjacent positions in a heterocyclic ring. An example of the latter is seen in 1,2,6-triphenylpyridinium salts, which undergo photochemical cyclization to give a bridgehead aza-derivative of triphenylene (3.67). 

Primary alkyl and benzyl fluorides are available from the corresponding primary amines via the pyridinium salts. Thus, pyrolysis of N-substituted 2,4,6-triphenylpyridinium fluorides and tetrafluoroborates, 2,4-diphenyl-5.6-dihydrobenzo[A]quinolinium tetrafluoroborates, and... 

Continuation of the work reported last year on the conversion of 2,4,6-triphenylpyrylium salts into the corresponding 2,4,6-triphenylpyridiniums has yielded additional synthetically useful procedures. Examples are the conversion of alkyl, aryl, and heteroaryl primary amines into iodides,esters, " and thiocyanates and the production of carbodi-imides from amidrazones, as outlined in Scheme 34. ... 

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