Bases pseudo

With W-substituted quaternary derivatives in the presence of oxidizing agents, ring opening is avoided and the classical Dekker oxidation of the pseudo-base occurs to give (45) (62JCS1671). 

Some pseudo bases are stable. 1,3-Dithiolylium adds alkoxide ions at the 2-position to give stable adducts which regenerate the starting salts with acids (80AHC(27)151). Pseudo bases can also lose water to give an ether (e.g. 167 -> 168). 

Oxidation to an azolone is an expected reaction for a pseudo base, but little appears to be known of such reactions. Most commonly, pseudo bases suffer ring fission. Estimated rates of ring-opening of (169) are in the ratio 10 10" 1 for X = O, S and NMe, respectively (79AHC(25)1). 

Thus quaternized thiazoles (170) consume two equivalents of OH on titration because the pseudo bases (171) ring open to (172), which form anions (173). Quaternized oxazoles (174) are readily attacked by hydroxide to give open-chain products such as (175) (74AHC(17)99), and quaternized 1,3,4-oxadiazoles behave similarly. Quaternary isothiazoles (e.g. 176) are cleaved by hydroxide (72AHC(l4)l), as are 1,2,4-thiadiazolium salts (177 178). 

Pyrimido[4,5-6]quinolinium salts pseudo bases - ring opening, 3, 208 Pyrimido[4,5-6]quinolinium salts, 4-chloro-hydrolysis, 3, 214 Pyrimido[4,5-6]quinolinones synthesis, 3, 228 Pyrimido[4,5 -6]quinolin-5-ones synthesis, 3, 221-222 Pyrimidothiadi azoles reactions, 6, 533 Pyrimidothiazines synthesis, 4, 527 Pyrimidothiazinones mass spectra, 2, 23... 

The study of structure and reactivity of tertiary heterocyclic enamines is associated with the problem of equilibrium of the cyclic enamine form (70) and the tautomeric hydration products 173,174) quaternary hydroxide (71), pseudo base (so-called carbinolamine) (72) and an opened form of amino aldehyde or amino ketone (73). 

Compound 74 belongs to a special group which forms cyclic aldehyde ammonia 75 (cotarnine) by interaction of the secondary amine group with the aldehyde group. This aldehyde ammonia can be considered to be a pseudo base. 

Hantzsch 2 gave the name pseudo bases to those carbinols that gave salts with acids by the elimination of water and a simultaneous change of constitution. Such carbinols are common among the nitrogen heterocyclic compounds and the naturally occurring alkaloids e.g., berberine, sanguinarine, chelerythrine. 

Recently Gadamer s view > has been widely accepted. He postulates for these compounds a tautomeric system of three components, in which the quaternary ammonium hydroxide, the pseudo base (or... 

In addition, pseudobasie carbinols are known with oxygen (oxonium pseudo bases) or with sulfur as hetero atom (sulfonium pseudo bases). 

Thus the following problems are unsolved (1) Does the threefold tautomerism assumed by Gadamer really exist for heterocyclic pseudo bases and which factors determine the stability of the various forms (2) Does ring-chain tautomerism occur in the derivatives of these bases when this is formally possible, and if not, do these derivatives possess the cyclic or open-chain structure, and by what path have they been formed ... 

Thus among the known pseudo bases derived from heterocyclic quaternary ammonium salts, the following principal types can be differentiated according to their basicity ... 

The heterocyclic pseudobasic carbinolamines show a very varied reactivity. However, the structure of a large number of their transformation products, in particular those from which conclusions have been drawn as to the structure of the initial pseudo base, are incorrect even in the most recent literature. 

Ingold makes no differentiation in principle between pseudo bases and those derivatives which are formed by the action of nucleophilic reagents. The latter he denotes by the general term "pseudo salts and considers their formation parallel to the formation of the car-binolamines themselves. If the mesomeric cation combines with a hydroxide ion, a pseudo base is formed if it combines with another nucleophilic ion or molecule, then a pseudo salt is formed. 

As an over-all conclusion, it can be stated that the assumption of ring-chain tautomerism in the pseudo bases derived from the heterocyclic quaternary ammonium salts is quite unnecessary as an explanation of the formation of two (cyclic and open-chain) types of deriva-... 

The structure of the unstable hydrated neutral molecule (4) was deduced from the similarity of its ultraviolet spectrum with that of tlie pseudo base (5), derived from (6) of known structure. This... 

First, mention should be made of the metathetical reaction, replacing an anion of a pyrylium salt by another-, when the solubility of the latter salt is lower than that of the former, the conversion is easy. In the opposite case, one has to find a solvent in which the solubilities are reversed (perchlorates are less soluble in water than chloroferrates or iodides, but in concentrated hydrochloric or hydroidic acids, respectively, the situation is reversed For preparing chlorides which are usually readily soluble salts, one can treat the less soluble chloroferrates with hydrogen sulfide or hydroxylamine. Another method is to obtain the pseudo base in an organic solvent and to treat it with an anhydrous acid. 

Only one electrophilic substitution at the pyrylium ring has been described, namely the j8-deuteration of 2,4,6-trimethylpyrylium or 2,4,fi-triphenylpyrylium perchlorates on prolonged reflux in CHjCOOD possibly, however, this reaction proceeds via the pseudo base. The nitration of 2,4,6-triphenylpyrylium does not affect the pyrylium ring, but attacks the 2- and 6-phenyl groups in the meta-, and the 4-phenyl group in the am-position, as was proved by... 

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