Photocyclization of 2‐[1]benzothien‐3‐yl)‐3‐phenylpropenoic acids

Photocyclization of the substituted 2‐([1]benzothien‐3‐yl)‐3‐phenylpropenoic acids 3a‐c in the presence of iodine and air in a benzene‐cyclohexane mixture afforded a separable mixture of three compounds, benzo[ b ]naphtho[2,1‐ d ]thiophene‐6‐carboxylic acids 4a‐c , 6 H ‐benzo[ b ]naphtho[2,3‐ d ]thiopyran‐6‐ones 5a‐c , and 10‐methoxy‐2‐methyl‐6 H ‐benzo[ b ]naphtho[2,3‐ d ]pyran‐6‐one ( 6 ).