20460-57-5Relevant academic research and scientific papers
SYNTHESIS OF PYRYLIUM SALTS WITH VARIOUS ANIONS
Dinculescu, A.,Balaban, T. S.,Popescu, Cristina,Toader, D.,Balaban, A. T.
, p. 665 - 672 (2007/10/02)
Four methods are described for obtaining pyrylium salts with various anions which influence strongly their solubility, their reactivity and ease of purification: (i) direct synthesis; (ii) conversion of pyrylium salt into its pseudobase (1,5-enedione) which is recyclised with the acid corresponding to the desired anion; (iii) anion metathesis and (iv) reductive stripping of the anion with sodium borohydride in carboxylic acid media which also provides a carboxylate anion.Method (iv) is new and is complementary to the direct metathesis (iii) because it allows the replacement of anions stemming from strong acids which confer insolubility to pyrylium salts with anions derived from much weaker acids and which give more soluble salts.The present paper also describes some new pyrylium salts obtained by all methods (i-iv).One may mention among these 2,4,6-trimethylpyrylium hydrogenisobutenedisulfonate which results directly from sulfuric acid, acetic anhydride and isobutene or t-butanol at temperatures below 30 deg C.
PYRYLIUM-MEDIATED TRANSFORMATION OF NATURAL PRODUCTS. PART 4. REACTIONS OF WATER-SOLUBLE PYRYLIUM SALTS WITH WATER AND WITH AMINES
Katritzky, Alan R.,Leahy, David E.
, p. 867 - 874 (2007/10/02)
Pyrylium cation equilibria and kinetics in aqueous solution have been measured and compared with existing data.Competing reactions of pyrylium cations with amines, water molecules, and hydroxide ions have been elucidated and rationalised.Conditions for maximising yields of pyrylium cations from pyrylium salts and amines in aqueous media have been deduced.
