Heterocyclische Siebenring‐Verbindungen, XXXVI. Synthese und Eigenschaften des 1,4‐Benzoxazepins und einiger monosubstituierter Derivate

Abstract

Heterocyclic Seven‐Membered Ring Compounds, XXXVI. — Synthesis and Properties of 1,4‐Benzoxazepine and of Some Monosubstituted Derivatives O ‐Alkylation of salicylamide with bromoacetaldehyde diethyl acetal and subsequent thermal ring closure yields the lactam 2 , which is converted into the imide chloride 3 . Pd(0)‐catalyzed dehalogenation of compound 3 with tributyltin hydride leads to the desired 1,4‐benzoxazepine ( 4 ), a thermally very unstable compound which prefers polymerization to valence isomerization. O ‐Alkylation of the lactam 2 and S ‐alkylation of the thiolactam 8 yield the 5‐substituted 1,4‐benzoxazepines 6 and 9 , resp., which are thermally considerably more stable than the parent compound 4 . Thus, they are capable of the expected thermal isomerization to the corresponding hydroxyisoquinolines 10 and 11 , resp. The photoisomerization of the 1,4‐benzoxazepines 4 , 6 , and 9 leads to the thermally very unstable dihydroazetes 12 , 13 , and 14 , of which only the methylthio compound 14 could be isolated as crystalline compound.