Synthesen mit Nitrilen, LVIII. Ein neuer Weg zu Isoxazolo[5,4‐ b ]pyridinen

Syntheses with Nitriles, LVIII. A New Route to Isoxazolo[5,4‐ b ]pyridines Reaction of dimeric malononitrile (2‐amino‐1‐propene‐1,1,3‐tricarbonitrile) ( 1 ) with benzo‐hydroximoyl chlorides in alkaline medium leads to substituted isoxazolo[5,4‐ b ]pyridines 6a – e . The isoxazole derivative 4a is an isolable intermediate. Condensation of the mixed dimer from malononitrile and methyl cyanoacetate (methyl 3‐amino‐2,4‐dicyanocrotonate) ( 3 ) with benzo‐hydroximoyl chlorides yields methyl 3‐amino‐3‐(5‐amino‐3‐aryl‐4‐isoxalyl)‐2‐cyanoacrylates ( 5a – c ). 6,7‐Dihydro‐6‐oxoisoxazolo[5,4‐ b ]pyridines 7a,c are obtained from 5a,c by elimination of alcohol.