Design And Synthesis Of Radical Catalyst Based On Intramolecular Electron Transfer

The free radical reaction, a wide-used organic reaction, has some superior characteristics to ion-type reactions. Developing of new type free radical catalyst can enormously extend the applications of radical reaction, and is of great potential in organic synthesis. Recently, the nitroxyl radical organocatalysts, such as N-hydroxyphthalimide (NHPI), received more and more attentions because of their excellent catalytic performance for radical reactions.This dissertation, based on the character of the nitroxyl radical catalysts, designed a new compound N-hydroxy-9,10-Anthraquinone-2,3-dicarboximide (NHADCI), which has a substructure of N-hydroxybisacylimide as the pre-radical group and a substructure of quinone carbonyl group as one-electron acceptor group. Between the two substructure, we expect the one-electron transfer could occurs, and yet forms nitroxyl radical for initiation of radical reaction.Two synthetic routes were designed, one uses pyromellitic dianhydride as starting material, the other uses o-xylene as starting material. Both of them have been employed successfully to synthesize 2,3-dicarboxyl-9,10-anthraquinone, an key intermediate of NHADCI. In comparison, the second is preferable.The formation NHADCI has been observed in its synthetic process including two steps of anhydridisation and bisacylimidation from 2,3-dicarboxyl-9,10-anthraquinone. However, NHADCI can not be isolated even using TLC because it is unsteady in solution. By acylation with acetic anhydride, NHADCI was captured successfully to obtain N-Acetoxy-9,10-Anthraquinone-2,3-dicarboximide.Theoretic calculation shows the bond dissociation energy of the O-H bond of NHADCI is 346.7 Kj/mol, which is lower than that of NHPI (356.2 Kj/mol). These results imply that the free radical from NHADCI, as expected, may be formed more easily via intramolecular electron transfer, which is likely to be the reason of its unsteadiness.Theπ~* orbital energy of nitroxyl radical of NHADCI was calculated to be -0.235 eV, much lower than that (-0.262 eV) of NHPI. These mean that itsπ* orbit accepts electron more easily in H-abstraction, and as a result NHADCI has probably a higher catalytic activity.