Synthesis of Some7 -Methoxy-2-(lH)-quinolone Derivatives

Reaction of 4-hydroxy-7-methoxy-2(lH)-quinolone (1) with iodosobenzenes, prepared in situ from the dichloroiodo compounds 2a,b, afforded the iodoniumylides 3a,b in good yields. Their thermal rearrangement produced the 3-iodo-4-aryloxy-quinolones 4a,b. Reductive -deiodinatton of 4a,b gave the corresponding arylethers 5a,b. By photocyclization 4a as well as 5a yielded the benzofuro-quinolone 6a (4b or 5b could not be cyclized to 6b). Acid catalyzed »transylidation« of the iodonium-ylides 3a,b with triphenylphosphane, pyridine and isoquinoline as nucleophiles produced the corresponding Pand N-ylides 8, 9a,b, respectively. The pyridinium(9a) and isoquinolinium-ylid (9b) were also prepared from the 3-chloro-4-hydroxy-2-quinolone 7a, which in turn could be obtained by the action of hydrochloric acid on 3a,b (7b was obtained by careful reaction of HBr with 3a).