Liquid-phase photolysis. Part XI. Stereochemistry of the photoaddition of maleic anhydride to benzene

Abstract

Conversion of the benzene–maleic anhydride 1:2 adduct, through a series of high-yield reactions, into a stable hydroxy-lactone-tricarboxylic acid has confirmed its formulation as tricyclo[4,2,2,0^2,5]dec-9-ene exo,endo-3,4:7,8-tetracarboxylic acid dianhydride. The orientation of the 1,2-photoaddition of maleic anhydride to benzene is therefore exo, whereas that of the 1,4-addition of a second molecule of maleic anhydride is endo. Both processes appear to be highly stereospecific.