2.6- Diphenylpyrylium perchlorate, reaction

Disubstituted ions 166 (R2 = R3 = R4 = H) provide, as rule only, 4H-pyrans 168 independent of the nature of the organometallic reactant RM. The reactions of 2,6-di-te/7-butylpyrylium perchlorate with f-BuMgCl or t-BuMgBr as well as of 2,6-diphenylpyrylium perchlorate or tetrafluoroborate with MeMgl, PhMgBr, PhCH2MgCl, and PhC=CLi were thus explored for... 

There are few examples of X-ray studies of pyrans. The product from the reaction of 2,6-diphenylpyrylium perchlorate with water in the presence of bases was shown to be the methylenepyran (155) by a combination of spectroscopic and crystallographic measurements (78T2131). 

Reactions of pentafluorophenyl-substituted pyrylium perchlorates with hydrazine hydrate are known to give 1,2-diazepines. 2-Pentafluorophenyl-4,6-diphenylpyrylium perchlorate reacts with hydrazine hydrate like the unfluorinated analogue, forming 3,5-diphenyl-7-pentafluorophenyMH-l,2-diazepine. However, the 2,6-di(pentafluorophenyl)-... 

A real counterpart to this imagined reaction course is the formation of 2-meth-oxy-4,6-diphenyl-2H-pyran (358) (99%) by treatment of 5-dimethylamino-l,4-diphenylpentadienone (212) with a small amount of hydrochloric acid in methanol. Addition of perchloric acid to (358) immediately precipitates 2,5-diphenylpyrylium perchlorate (357) and conversely, base and methanol reform (358) from (357) ... 

New uses for pyrylium salts include their reaction with azo-methines and ammonia to give 4-aminopyridines [e.g., (22)],37 with dimethylsulphonium methylide to yield the phenol (23) and with the anion of nitromethane to form the nitrophenol (24).38 The addition of lithium phenylacetylene to 2,6-diphenylpyrylium perchlorate in boiling ether has now been shown to form the pyran (25) but in THF at room temperature a dimeric product (26) is obtained.39 Its... 

Pyrylium salts undergo some interesting reactions for example, addition of methoxide ion, which may occur at C-2 or C-4, according to the structure of the substrate. The rates of some of these reactions in buffers have been measured spectrophotometrically and the behaviour of the salts has been explained in electronic and structural terms. 2,6-Diphenylpyrylium perchlorate reacts with tributyl phosphite (by an Arbuzov rearrangement) to give a high yield of the phosphite (71). °... 

The reaction between benzene and AQV-dimethylaniline N -oxide in the presence of CF3SO3H gives mainly (64—76%) 4-(AW-dimethylamino)biphenyl, probably via protonation on oxygen and loss of water to the JVN-dimethyl-immonium-benzenium ion. ° Treatment of ferrocene with 2-carboxy-4,6-diphenylpyrylium perchlorate yields the 2-ferrocenylpyrylium salt with decar-boxylation. ° ... 

A detailed study of this dehydrogenative condensation in the presence of triphenylmethyl perchlorate or fluoroborate was made by Simalty-Siemiatycki and Fugnitto. The reaction is best carried out in refluxing acetic acid nitromethane or acetonitrile give less satisfactory results. Chalcone reacts in these conditions with phenylacet-aldehyde yielding 2,4-diphenylpyrylium with an unsubstituted a-position. This and similar 2-unsubstituted pyrylium salts prepared by this method are so reactive that they do not afford pyridines on treatment with ammonia in the usual conditions this behavior is similar to that of the unsubstituted pyrylium perchlorate. The reaction of... 

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