Hydrogenation of substituted 1‐arylisoquinolin‐3(2 H )‐ones to 5, 6, 7, 8‐tetrahydro‐ and 1, 4‐dihydroisoquinolin‐3(2 H )‐ones

Catalytic hydrogenation of variously substituted 1‐arylisoquinolin‐3(2 H )‐ones 1 gave, depending on the substituents, 5, 6, 7, 8‐tetrahydroisoquinolin‐3(2 H )‐ones ( 2 ) and/or the corresponding 1, 4‐dihydro derivatives 3 . Saturation of the compounds fused with benzene ring furnished as the main products the 9, 10‐dihydro‐ ( 4 and 5 ) and 5, 6‐dihydroisoquinolin‐3(2 H )‐ones ( 6 ) in the case of benzo[ f ] and benzo[ h ] anellation, respectively, in addition to the 1, 4‐dihydro compounds detected or isolated as by‐products.