Studies on ketene and its derivatives. CXI . Photoreaction of diketene with 2(1 H )‐quinolone derivatives

Photoreaction of diketene with 4‐methyl‐2(1 H )‐quinolone and 1,4‐dimethyl‐2(1 H )‐quinolone gave 2 R *,2a R *,Sb R *‐ and 2 R *,2a S *8b S *‐8b‐methyl‐3‐oxo‐1,2,2a,3,4,8b‐hexahydrocyclobuta[c]quinoline‐2‐spiro‐2′‐(oxetan)‐4′‐one ( 6a and 6b ), and their 4‐methyl derivatives 7a and 7b , respectively. Thermolysis of compounds 6 and 7 afforded 2a R *,8b S *‐8b‐methyl‐2‐methylene‐3‐oxo‐1,2,2a,3,4,8b‐hexahydrocyclobuta[c]quinoline ( 8 ) and its 4‐methyl derivatives 9 , respectively. Similarly, photolysis of diketene and 4‐acetoxy‐2(1 H )‐quinolone gave 1 R *,2a S *,8b S *‐ and 1 R *,2a R *,8b R *‐8b‐acetoxy‐3‐oxo‐1,2,2a,3,4,8b‐hexahydrocyclobuta[ c ]‐quinoline ( 11a and 11b ). Alcoholysis of compounds 11a and 11b with hydrogen chloride in methanol gave 1‐hydroxy‐1‐(methoxycarbonyl)methylcyclobuta[ c ]quinoline derivative 12 and 13 which were transformed to 4‐acetyl‐3‐methyl‐2(1 H )‐quinolone ( 15 ) by further alcoholysis. Photoreaction of diketene with 2(1 H )‐quinolone derivatives gave the corresponding cyclobuta[c]quinoline spirooxetanone derivatives 18 and 23 , which, by thermolysis, were transformed to 2‐methylenecyclobuta[ c ]quinoline 23 and 25 , respectively.