Benzocyclobutene

Benzocyclobutene
Skeletal formula
Ball-and-stick model
Names
Preferred IUPAC name
Bicyclo[4.2.0]octa-1,3,5-triene
Other names
Benzocyclobutane
BCB
Benzocyclobutene (not in accordance with IUPAC nomenclature)
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.161.355
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C8H8/c1-2-4-8-6-5-7(8)3-1/h1-4H,5-6H2 ☒N
    Key: UMIVXZPTRXBADB-UHFFFAOYSA-N ☒N
  • InChI=1/C8H8/c1-2-4-8-6-5-7(8)3-1/h1-4H,5-6H2
    Key: UMIVXZPTRXBADB-UHFFFAOYAR
SMILES
  • C12=CC=CC=C1CC2
Properties
Chemical formula
 C8H8
Molar mass 104.152 g·mol−1
Density 0.957 g/cm3
Boiling point 150 °C (302 °F; 423 K)
Refractive index (nD)
 1.541
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Benzocyclobutene (BCB) is a benzene ring fused to a cyclobutane ring. It has chemical formula C8H8.[1]

BCB is frequently used to create photosensitive polymers. BCB-based polymer dielectrics may be spun on or applied to various substrates for use in Micro Electro-Mechanical Systems (MEMS) and microelectronics processing. Applications include wafer bonding, optical interconnects, low-κ dielectrics, or even intracortical neural implants.

Reactions

Benzocyclobutene is a strained system which, upon heating to approximately 180 °C, causes the cyclobutene to undergo a conrotatory ring-opening reaction, forming o-xylylene. Since this process destroys the aromaticity of the benzene ring, the reverse reaction is highly favored.

Thermal generation of o-xylylene from benzocyclobutene
Thermal generation of o-xylylene from benzocyclobutene

o-Xylylenes generated in this way have been used prolifically in cycloaddition reactions, which restore the aromaticity to the benzene ring, while forming a new annulated species.[2]

Derivatives

The benzocyclobutene moiety has also appeared in a number of chemical compounds with pharmacological properties such as ivabradine and S33005.

Additionally, cyclized phenethylamine psychedelic drugs containing the benzocyclobutene ring system, including TCB-2, tomscaline, bromotomscaline, and 2CBCB-NBOMe (NBOMe-TCB-2), have been described.[3] A benzocyclobutene-derived amphetamine has been patented as well,[4] and a benzocyclobutene containing designer drug, the substituted cathinone derivative 3,4-EtPV, has been sold in Europe.[5] The benzocyclobutene derivative 2C-G-2 has also been claimed in a patent as an antiinflammatory,[6] but no synthesis or activity data is provided so it is unclear if it has actually been made.

See also

  • Benzocyclobutadiene

References

  1. ^ 164410 Benzocyclobutene 98%
  2. ^ Mehta, G.; Kotha, S. (2001). "Recent chemistry of benzocyclobutenes" (PDF). Tetrahedron Lett. 57 (4): 625–659. doi:10.1016/s0040-4020(00)00958-3.
  3. ^ Trachsel, D.; Lehmann, D.; Enzensperger, C. (2013). Phenethylamine: von der Struktur zur Funktion [Phenethylamines: From Structure to Function]. Nachtschatten-Science (in German) (1 ed.). Solothurn: Nachtschatten-Verlag. ISBN 978-3-03788-700-4. OCLC 858805226. Archived from the original on 12 August 2025. Retrieved 30 November 2025.{{cite book}}: CS1 maint: bot: original URL status unknown (link)
  4. ^ US 3149159, "Substituted 7-aminoalkylbicyclo-[4. 2. 0]octa-1,3,5-trienes" 
  5. ^ "European Drug Report 2025 – Full Book" (PDF). European Union Drugs Agency (euda.europa.eu). 6 June 2025.
  6. ^ Halpert M. Substituted phenethylamine for treating inflammation and psychological disorders. WO 2022/271982
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