Benzo phenanthridones synthesis

Begley and Grimshaw (94) reported a modified synthesis of nitidine (77) by shortening the steps in Kessar s route (88) by using the A -methylbenza-mide (93) under photochemical conditions. However, they failed to obtain benzo[c]phenanthridone by electrochemical means (94) (Scheme 47). 

Isoquinoline-1,3,4-triones are useful intermediates for the synthesis of benzo[c]phenanthridones in about a 30% yield in a three step sequence which utilises... 

The photocyclisation of A-phenyl-3-vinylquinolin-2( )-ones provides a facile route to benzo[k]phenanthridones. Under non-oxidative conditions, the tetrahydro derivative results, but photolysis in the presence of iodine gives the fully aromatic heterocycle. Introduction of a 2-chlorine substituent into the starting material results in the formation of 6-chloro-7,8-dihydrobenzophen-anthridones (K. Veeramani et al.. Synthesis, 1978, 855). 

Photolysis of styrylquinolones (130) affords benzo-[k]phenanthridones whilst the benzylidene lactones (131), from which the styrylquinolones may be prepared, give 6-oxobenzo[k]phenanthridine-7-carbo3 1ates on irradiation in methanol (V. Arisvaran et al,. Synthesis, 1981, 821). 

With N-methylbenzamides, the yields of substitution products are lower. > The S j l reaction between substituted o-iodobenzamides and the enolate anion of 2-acetylhomoveratic acid can be used for the synthesis of derivatives of the benzo(c)-phenanthridone and berberine alkaloids. ... 

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