Aromatic Radical-Induced Intramolecular Aromatic 1,5-Hydrogen Transfer

A series of diazonium salts of 4-phenoxy-3-amino-1, 8- naphthalic anhydride derivatives 5a-h were designed and synthesized, and they produced the corresponding two isomers-five-membered compounds 9 and six-membered compounds 10, which demonstrated that the aromatic radical-induced aromatic 1, 5-hydrogen transfer was involved in the system during Pschorr cyclization.In the case of oxygen as bridge atom, in the phenoxy naphthalic anhydride system no more than 10% rearrangement (10a and 10d) was observed, while in the phenoxy naphthalimide systems the rearranged products increased to more than 20% (10b 23%, 10c 21%, and 10e 34%). In fact reducing the electron-withdrawing capacity of naphthalene ring by amination of naphthalic anhydride or increasing the electron-withdrawing capacity of benzene ring, which reduced the difference of electron density between the two interacting aromatic system, is propitious to the hydrogen-transfer.In the case of sulfur as bridge atom, whether the naphthalic anhydride diazonium salt (5f) or the naphthalimide diazonium salts (5g and 5h), their rearrangement (10f, lOg and 10h) were no more than 10% of the total ring-closed product via Pschorr cyclization. However, the yields of the total ring-closed products of naphthyl phenyl thioether system were much higher than that of naphthyl phenyl ether system, in other words, ring-closed rate of them is much faster than that of the former naphthyl phenyl ether system, and the rapid ring-closed rate weakened the effect of the variant rate of H-transfer.Diazonium salts of 4-(N-methyl-N-phenylamino)-3-amino-l, 8- naphthalic anhydride 5i and its naphthalimide derivative 5j were designed and synthesized, and it was the first time to discover that aromatic radical-induced aromatic 1, 5-hydrogen transfer was also involved in the nitrogen-contained system during Pschorr cyclization. In addition, the ratios of rearranged isomers increased from 9%(10i) to 14%(10j) as reducing the dispersion of electron density between the two interacting aromatic system.Diazonium salts of 4-(2-amino-phen(thio)oxy)-3-amino-l, 8- naphthalic anhydride 8a and 8f were designed and synthesized, and they also produced the corresponding two isomers-- five-membered compounds 9a(f) and six-membered compounds 10a(f), and the amount of six-membered compounds is large than that of five-membered compounds whichdemonstrated that radical B is easier to form six-membered rings than to form five-membered rings.