1,1'-Thiocarbonyldiimidazole (TCDI) is a thiourea containing two imidazole rings.

[1] It is the sulfur analog of the peptide coupling reagent carbonyldiimidazole (CDI).

TCDI is commercially available but can also be prepared via the reaction of thiophosgene with two equivalents of imidazole.

[1] The imidazole groups on TCDI can be easily displaced, allowing it to act as a safer alternative to thiophosgene.

[2] It may also replace carbonothioyl species (RC(S)Cl) in the Barton–McCombie deoxygenation.