2 -Quinoxalinone complexes

Note These are only a few typical examples of the complexes formed by tautomeric quinoxalinones. 

Quinoxalinone charge-transfer complexes with tetrachloro-l,4-benzoqui-... 

The major reactions in this section are those involving an V-oxide oxygen. Deoxygenation of 2,3-disubstituted quinoxaline 1,4-dioxides is achieved under mild conditions by treating with hexa-chlorodisilane, TMS-1, TFAA-sodium iodide, or titanium tetrachloride-zinc dust <81H(i6)4ii>. Quinoxaline and phenazine V,A( -dioxides are also deoxygenated under mild conditions by sodium hypophosphite catalyzed by Pd/C or by treatment with sodium iodide in the presence of pyri-dine/sulfur trioxide complex <83JHC1735>. Deoxygenation of 6-chloro-2(l//)-quinoxalinone 4-oxide is effected particularly by sodium borohydride or sodium hydrosulfite <85H(23)143>. 

The formation of unsubstituted quinoxaline 1,4-dioxide in the Beirut reaction has been observed using a number of substrates benzoylacetalde-hyde and its enamines,395 vinyl acetate (Et2NH),396 acetylene (NEt3)397,398 propargyl alcohol, propiolic acid, and phenylacetylene (various amines).398 Some of these are unexceptional, but the apparent dephenylation in the case of the phenylacetylene is surprising. However, recently the reaction of benzofuroxan with diethylamine was reinvestigated399 (see Section V,E), and quinoxaline dioxide was found to be one of the major products from a complex sequence of oxidation and reduction reactions. It seems probable with phenylacetylene, and possible in other cases too, that the amines play more than a catalytic role in quinoxaline dioxide production. The amino-quinoxalinone 175 was reported, using vinyl acetate and morpholine.396... 

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