Discover the reaction hidden in the solution to this sudoku-inspired puzzle

Solve this wordoku in the same way as a sudoku with letters instead of numbers (each of the nine letters in each row, column and nine-square cell). Once solved, one of the overall diagonals can be rearranged to give the name of a reaction in which primary amines are converted into pyridinium salts.

This week’s letters are: A E I K R S T Y Z