Photolyse von 3‐Methyl‐2, 1‐benzisoxazol (3‐Methylanthranil) und 2‐Azido‐acetophenon in Gegenwart von Schwefelsäure und Benzolderivaten

Abstract

Photolysis of 3‐Methyl‐2, 1‐benzisoxazole (3‐Methylanthranil) and 2‐Azido‐acetophenone in the Presence of Sulfuric Acid and Benzene Derivatives Irradiation of 3‐methylanthranil (1) in acetonitrile in the presence of sulfuric acid and benzene, toluene, p‐xylene, mesitylene or anisole with a mercury high‐pressure lamp through a pyrex filter yields beside varying amounts of 2‐amino‐acetophenone (3) and 2‐amino‐5‐hydroxy‐ (4a) and 2‐amino‐3‐hydroxy‐acetophenone (4b) the corresponding diphenylamine derivatives 5 (see Table 1). In the case of toluene and anisole mixtures of the corresponding ortho‐ and para‐substituted isomers (5b, 5d or 5g, 5i respectively), but no meta‐substituted isomers (5c or 5h) are obtained. In addition to these products, the irradiation of 1 in the presence of anisole yields also 2‐amino‐5‐(4′‐methoxyphenyl)‐acetophenone (7), 2‐amino‐3‐(4′‐methoxyphenyl)‐acetophenone (8) and 2‐methoxy‐9‐methyl‐acridine (6; see Scheme 1). The latter product is also formed thermally by acid catalysis from the diphenylamine derivative 5i. Irradiation of 2‐azido‐acetophenone (2) in acetonitrile solution in the presence of sulfuric acid and benzene leads to the formation of 1, 3, 4a, 4b, 5a and 9 (see Table 2). Compounds 3, 4a, 4b and 5a are also obtained after acid catalyzed decomposition of 2 in the presence of benzene. Thus, it is concluded that irradiation of 1 or 2 in the presence of sulfuric acid yields 2‐acetyl‐phenylnitrenium ions 10 in the singlet ground state which will undergo electrophilic substitution of the aromatic compounds, perhaps via the π‐complex 11 (see Scheme 2).