Benzocyclobutene (BCB) is a benzene ring fused to a cyclobutane ring. It has chemical formula .
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.
center|400px|class=skin-invert-image|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.
Derivatives
Cyclized phenethylamine psychedelic drugs containing the benzocyclobutene ring system, including TCB-2, tomscaline, bromotomscaline, and 2CBCB-NBOMe (NBOMe-TCB-2), have been described. A benzocyclobutene-derived amphetamine has been patented as well, and a benzocyclobutene containing designer drug, the substituted cathinone derivative 3,4-EtPV, has been sold in Europe. The benzocyclobutene derivative 2C-G-2 has also been claimed in a patent as an antiinflammatory, but no synthesis or activity data is provided so it is unclear if it has actually been made.
The benzocyclobutene moiety also appears in the FDA approved medication ivabradine.
See also
- Benzocyclobutadiene