CHEMICAL SYNTHESES OF SYN-1,2-3,4-DIEPOXIDES AND ANTI-1,2-3,4-DIEPOXIDES DERIVED FROM 1,4-DIMETHYLANTHRACENE AND 1,2,3,4-TETRAMETHYLANTHRACENE AND 1,4-DIMETHYLNAPHTHALENE AND 1,2,3,4-TETRAMETHYLNAPHTHALENE

Chemical isomerization of 1,4-endoperoxides la,b,n derived from meso-u nsubstituted 1,4-dimethyl-or 1,2,3,4-tetramethylanthracenes (and napht halenes) to syn-1,2;3,4-diepoxides aa,b,n has been achieved by treatme nt at room temperature with FeSO4 in CH3CN containing pyridine. With a nalogous 9,10-diphenyl derivatives Ic,d, heating appears necessary and the same isomerization is then superseded by another type of rearrang ement leading to dihydronaphthoxanthenols 4c,d. An electron-exchange m echanism may explain the difference between both series. In contrast, the isomeric anti-1,2;3,4-diepoxides 19b,c,d,n have been prepared by d irect epoxidation of the hydrocarbons 18a-d,n with dimethyldioxirane g enerated in situ. In this case, the reaction is more efficient for 9,1 0-diphenyl derivatives 18c,d than for meso-unsubstituted ones 18a,b as the latter can undergo competitive oxidations at meso-positions leadi ng to 10-hydroxy-9-anthrones 22a,b at the same time as anthraquinones 23a,b.