Japp-Klingemann Reaction

F. R. Japp, F. Klingemann, Ann. 247, 190 (1888); Ber. 20, 2942, 3284, 3398 (1887).

Formation of hydrazones by coupling of aryldiazonium salts with active methylene compounds in which at least one of the activating groups is acyl or carboxyl. This group usually cleaves during the process:

Review: R. R. Phillips, Org. React. 10, 143 (1959); H. C. Yao, P. Resnick, J. Am. Chem. Soc. 84, 3504 (1962); M. O. Lozinskii, A. A. Gershkovich, ibid. 8, 785 (1972); A. Kozikowski, W. C. Floyd, Tetrahedron Letters 1978, 19. Use of brominium ion as leaving group: G. Cirrincione et al., J. Heterocyclic Chem. 27, 983 (1990). Synthetic applications: F. Chetoni et al., ibid. 30, 1481 (1993); B. Loubinoux et al., J. Org. Chem. 60, 953 (1995); B. Pete et al., Heterocycles 53, 665 (2000).