semicarbazones

https://doi.org/10.1351/goldbook.S05589

Compounds having the structure R₂C=NNHC(=O)NH₂, formally derived by condensation of aldehydes or ketones with semicarbazide [NH₂NHC(=O)NH₂].

Source:
PAC, 1996, 68, 1361. 'Functional dyes from nature: Potentials for technical applications' on page 1365 (https://doi.org/10.1351/pac199668071361)