Applications of Benzo[c]Furans

Benzo[c]furan, also known as isobenzofuran, is a planar unique class of o-quinonoidal bicyclic monooxygen heterocycles with a 10π electron ring system in which the benzene ring is annulated at 3,4-positions of the π-excessive  furan ring. The resonance energy of benzo[c]furan is much less than that of benzo[b]furan and as a consequence it is  very reactive, unstable, and rapidly polymerizes even at low temperature. Due to instability of the parent benzo[c] furan, the pure compound has not been isolated. The stability of such molecules is being increased by introducing  special electron-withdrawing substituents at the 1- and 3-positions of benzo[c]furan. Additional stability can also  be introduced by benzannulation at 4,5 or 6,7 double bonds. The transient existence of benzo[c]furans has also been  confirmed by trapping with a dienophile in situ as a [4+2] cycloadduct.

Physical Properties 

The most stable 1,3-diphenylbenzo[c]furan is a yellow crystalline solid with an mp of 127°C. Its solution has a  blue-green fluorescence. Mostly, unsubstituted benzo[c]furans have transient existence and are trapped in situ with  dienophiles to give isolable cycloadducts.

Applications of Benzo[c]Furans 

Benzo[c]furan derivatives have important luminescent and electroluminescent properties. Hexaphenylbenzo[c] furan has been incorporated into organic light-emitting diode devices. It has been used as a reagent of choice for trapping and characterizing transient alkenes and alkynes. Benzo[c]furan has also been used to quantitatively measure  the rate of singlet oxygen generation in biological systems.

Synthesis

By Pyrolysis of Benzyne-Furan Cycloadducts The reduced benzyne-furan cycloadducts on flash vacuum pyrolysis at 600°C gave transient benzo[c]furan with  elimination of ethane as a by-product.