1,5 Diazabicyclo(4.3.0)non 5 ene

1,5-Diazabicyclo[4.3.0]non-5-ene (DBN) is a chemical compound with the formula C₇H₁₂N₂. It is an amidine base used in organic synthesis. A related compound with related functions is 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). The relatively complex nature of the formal names for DBU and DBN (hence the common use of acronyms) reflects the fact that these compounds are bicyclic and contain several functional groups.

The compounds are employed for dehydrohalogenation reactions as well as base-catalyzed rearrangements.