Photolysis of the azo‐precursors of 2,3‐ and 1,8‐naphtoquinodimethane. Preliminary communication

Abstract

Abstract A novel oxidation method for the synthesis of labile azo‐alkanes is reported. Matrix‐isolated 2,3‐naphthoquinodimethane is obtained by photolysis of 1,4‐dihydrobenzo[ g ]‐phthalazine in a rigid matrix (EPA glass) at 77 K and the electronic structure of its ground and lowest excited states is discussed. Nitrogen elimination from 1,4‐dihydronaphtho[1,8‐ de ][1,2]‐diazepine to yield acenaphthene occurs exclusively upon ππ* excitation while irradiation in the n‐π* absorption region induces cis/trans isomerization of the azo‐moiety. Neither ns flash nor low‐temperature photolysis provide evidence for the occurrence of 1,8‐naphthoquinodimethane as an intermediate in the formation of acenaphthene.