1- in a search directed to the reaction of compound)23(the cycloaddition reaction of 1,3- diphenylisobenzofurane)14(with p-benzoquinone)19(,followed by addition of cyclopentadiene was carried out.the specific spacial stracture of its ir,nmr,mass spectra. 2- in another attempt the kinetic stability and behavior of compounds)20(and)23(was studied.the main subject of this study was the highly reversibility of these compounds and their similar counterparts and compounds at various temperature in different solvents.effort was centered on two conditions: in the first at room temperature compound)14(was treated with diketon to yieled compunds)20(and)23(.in the second , the temperatur was kept below zero in orther to minimise the retro-cycl-oaddition reaction.extensive studies revealed that both compounds)20(and)23(are capable to undergo retro addition reaction. 3- in a search for finding a condition to stop the retro - reaction or to stabilize compouns)20(and)23(,effort was subjected toward reduction of one of the keto groups of these compounds.there for treatment of diketone solution)in both previos conditions(with sodium borohydrid led to a monoreduction product. the remarkable properties of the reduction products are their highly stability toward retro-diels-alder reaction.the actual factor effectin thier specific property and those factors which are the cause of unstability of compouns)20(and)23(are fully discused in the text.