1,8-Diazabicyclo(5.4.0)undec-7-ene

1,8-Diazabicyclo[5.4.0]undec-7-ene, or more commonly DBU, is a chemical compound and belongs to the class of amidine compounds. It is used in organic synthesis as a catalyst, a complexing ligand, and a non-nucleophilic base.

Synthesis

DBU can be synthesised in three steps from caprolactam and acrylonitrile. First, the nitrile undergoes an addition reaction at the caprolactam nitrogen, producing N-(2-cyanoethyl)-caprolactam. This is then hydrogenated to N-aminopropyl-caprolactam, followed by an intramolecular carbonyl condensation to form the imine. Water is removed by fractional distillation.

Occurrence

Although all commercially available DBU is produced synthetically, it may also be isolated from the sea sponge Niphates digitalis. The biosynthesis of DBU has been proposed to begin with adipaldehyde and 1,3-diaminopropane.

File:REGALADO DBU BIOSYNTHETIC HYPOTHESIS.png

Proposed pathway for the biosynthesis of DBU in sponges.

Applications

DBU is used:

• As a reagent in organic chemistry, where DBU is used as a ligand and base. As a base, protonation occurs at the imine nitrogen. Lewis acids also attach to the same nitrogen.
• As a catalyst, for example as a curing agent for epoxy resins and polyurethane.
• In the separation of fullerenes in conjunction with trimethylbenzene. It reacts with C₇₀ and higher fullerenes, but not with C₆₀.
• As a dehydrohalogenation agent.
• In surface activation products (primers) for low-surface energy plastics and elastomers (such as PTFE, HDPE, PP, and silicone rubber), where DBU raises the surface energy enough for adhesives (such as cyanoacrylate and contact cement) to bond to these otherwise inert, non-stick materials.

See also

• 1,5-Diazabicyclo[4.3.0]non-5-ene
• DABCO