Internuclear cyclisation. Part XXIX. Oxidation of some N-methylbiphenyl-2-carboxamides with persulphate

Abstract

Oxidations of 2′-, 3′-, and 4′-methoxy-N-methylbiphenyl-2-carboxamides by potassium persulphate have been studied. Cyclisation to γ-lactams as well as the expected phenanthridinones is found to be important, particularly in alkaline solution. Similar oxidation of N-methylbiphenyl-2-carboxamide itself in alkaline solution in the presence of oxygen gives some of the γ-lactam-dienone (16) in addition to N-methylphenanthridinone. Persulphate oxidation of 3-methoxy-N-methylphenanthridinone gives the biphenanthridinone (20).