Oxidative conversions of 2,2'-diphenoquinone valence isomers with 2,3-dichloro-5,6-dicyanobenzoquinone. Synthesis and spectroscopic properties of (E)-(3,3')dibenzofuranylidene-2,2'-diones (isoxindigos)
Oxidative conversions of 2,2'-diphenoquinone valence isomers with 2,3-dichloro-5,6-dicyanobenzoquinone. Synthesis and spectroscopic properties of (E)-(3,3')dibenzofuranylidene-2,2'-diones (isoxindigos)
3-hydroxy-3H-benzofuran-2-ones afford when treated successively with thionyl chloride and triethylamine the otherwise difficult to make (E)-[3,3′]bibenzofuranylidene-2,2′-diones (isoxindigos). Access to the starting 3-hydroxy-3H-benzofuran-2-ones is easily achievable by reaction of properly substituted phenols with glyoxylic acid.
Dibenzonaphthyrone of formula (I)
1
wherein A
1
and A
2
independently of each other are unsubstituted or mono- to tetra-substituted o-C
6
-C
18
arylene, with the proviso that formula (I) does not represent a dibenzonaphthyrone of the formula
2
The invention further relates to processes for the preparation thereof, to the use thereof for colouring/pigmenting high-molecular-weight organic material and to substance compositions comprising dibenzonaphthyrones.