A PHOTOCHEMICAL REACTION OF 2-ALKOXY-3-BROMO-1,4-NAPHTHOQUINONE WITH 1,1-DIARYLETHYLENE—A NOVEL SYNTHETIC METHOD OF 5-ARYL-7,12-BENZ (a) ANTHRAQUINONES
The divergent preparation of 1,4-naphthoquinones and tetraphene-7,12-diones, which bear the ABCD-ring of landomycins, has been accomplished directly through oxidative reorganization of previously non-isolable cyclobuta[a]naphthalen-4(2H)-ones.
In spite of large steric repulsion betweenaromaticquinone moiety and dicyanomethylene moiety the title compounds (BDCNBA) were synthesized by TiCl4-catalyzed reactions of the corresponding aromaticquinones and malononitrile. BDCNBA showed electronic spectra indicating the intramolecular charge-transferinteraction and redox properties similar to 11,11,12,12-tetracyano-9,10-anthraquinodimethane (TCNAQ)
By the photolysis of the benzene solution of a variety of 2,3-disubstituted (halogeno, methoxy, and acetoxy) 1,4-naphthoquinones, 1, and 1,1-diarylethylenes, 2, 5-aryl-7,12-benz[a]anthracenediones, 3, are obtained in fairly good yields (22–68%).
photoreactions of 2-chloro-, 2-bromo-, 2,3-dichloro- and 2,3-bromo-1,4-naphthoquinones with arylethenes are dependent on the addend structure. Cyclobutane adducts are formed from styrene, 1,1-diphenylethene undergoes photosubstitution to give photolabile 1,1-diphenyl-1,3-diene derivatives, and spiro-oxetanes are the main products with trans-stilbene. 2-Acetoxy-1,4-naphthoquinone undergoes efficient (2π + 2π)