Synthesis of Trans ‐4 a ,12 b /3,4‐Dihydrodibenzo[ f , h ]quinolin‐2(1 H )‐Ones and Dibenzo[ f , h ]quinolin‐2(1 H )‐Ones via Irradiation of 6‐Biphenylpyridine‐2(1 H )‐Ones

The synthesis of trans ‐4 a ,12 b ‐dihydrodibenzo[ f , h ]quinolin‐2(1 H )‐ones ( 2) , dibenzo[ f , h ]quinolin‐2(1 H )‐ones (3) and 3,4‐dihydrodibenzo[ f , h ]quinolin‐2(1 H )‐ones ( 4) via photo‐induced annulation of 6‐([1,1′‐biphenyl]‐2‐yl)pyridine‐2(1 H )‐ones ( 1) under irradiation of a 313 nm UV light was described. Compounds 2 were obtained in 82–95% yields when the irradiation time was 3 h. Products 3 were obtained by irradiating 1 for 12 h in the presence of iodine. Heating the solutions of 2 in DMF at 130 °C for 24 h gave compounds 4 via a double 1,3‐H shift. The demonstrated protocols showed the diversity of photo‐induced cyclization of compounds 1 .