Claisen ‐Umlagerung von 2‐Propinyl‐(3‐pyridyl)‐und Allyl‐(3‐pyridyl)äthern

Claisen Rearrangement of 2‐Propinyl (3‐Pyridyl) and Allyl (3‐Pyridyl) Ethers Verbindungen vom Typ 1 werden mit Ausnahme von 17 und 25 als Äther benannt. Der systematische Name von 1 ist: 3‐(2‐Propinyl)oxy‐pyridin. 2‐Propinyl (3‐pyridyl) ether ( 1 ), synthesized from the corresponding 3‐pyridinol, was heated in DMF or decane at 208° in a sealed tube. In this way the furopyridines 2 and 3 were formed, and furthermore the pyranopyridine 4 if decane was used as solvent ( Scheme 1 ). The same reactions took place with (2‐methyl‐3‐pyridyl) 2‐propinyl ether ( 14 ). In DMF only 15 , and in decane 16 as well as 15 were formed ( Scheme 3 ). The rearrangement of the pyridine derivative 17 , which is substituted in both O ‐positions to the ether moiety, gave in both DMF and decane the diastereoisomeric tetracyclic compounds 18 and 19 . The same kind of reaction took place with 25 ( Scheme 4 ). In the thermolysis of the allyl 3‐pyridyl ether ( 27 ) cyclization was observed, too. The isolated product has the structure of the dihydrofuropyridine 28 ( Scheme 6 ). The substituted allyl 3‐pyridyl ether 30 reacted in the same way to the dihydrofuropyridine 31 ( Scheme 6 ).