Bradsher pyridinium salt synthesis

What is Bradsher pyridinium salt synthesis?

Bradsher discovered this reaction in 1955. The Bradsher pyridinium salt synthesis enables the production of heterocycles containing a pyridinium ring, such as oxazole[3,2-a]pyridinium, thiooxazole[3,2-a]pyridinium, and acridizinium salt.

Bradsher pyridinium salt synthesis
Bradsher pyridinium salt synthesis

R = H, alkyl, aryl
X = Cl, Br, I, etc.
The resulting quaternary ammonium salts serve as crucial and versatile intermediates in the creation of complex heterocyclic skeletons, which are utilized in pharmaceutical and materials chemistry.

For instance, acridizinium salts are commonly used in the Bradsher cycloaddition, and the oxazole[3,2-a] pyridinium can undergo ring opening from either the 5-membered ring when reacting with alkali, hydrosulfide H2S, ammonia and primary amines, CH-acids, etc. or the 6-membered ring in reaction with secondary amines.


  • Bradsher, C. K. and Beavers, L. E., J. Am. Chem. Soc., 1955, 77, 4812.
  • Bradsher, C. K. and Zinn, M., J. Heterocycl. Chem., 1967, 4, 66.
  • Bradsher, C. K.; Brandau, R. D.; Boilek, J. E. and Hough, T. L., J. Org. Chem., 1969, 34, 2129.
  • Bradsher, C. K., Acc. Chem. Res., 1969, 2, 181.
  • Bradsher, C. K.; Solomons, T. W. G. and Vaughan, F. R., J. Org. Chem., 1960, 25, 757.
  • Bradsher, C. K. and Westerman, I. J., J. Org. Chem., 1978, 43, 3536.