Japp–Klingemann reaction

[1][2][3][4][5][6] The reaction is named after the chemists Francis Robert Japp and Felix Klingemann.

The hydrazone products of the Japp–Klingemann reaction are most often used as intermediates in syntheses of more complex organic molecules.

[7][8] If there is a leaving group elsewhere in the Japp–Klingemann product, the hydrazone instead can cyclize at that site via a substitution reaction to give a pyrazole.

This process is a key part of the synthesis of pyraclofos [de] and related compounds:[9]

The nucleophilic addition of the enolate anion 2 to the diazonium salt produces the azo compound 3.