The cyclization reactions with CH3S03H/P20s (PPW) or CF3S03H/ Pz05 (PPTW) at 80-100 " C for 3-10 min afforded several heterocycles (6.7-dihydropyrrolo[2.3-~azepin-4.8(1~,5H)-dione.4-0x0-4.5.6.7-tetrahydrothianaphthene,carbostyril derivatives).On the research of developments for more effective cyclization procedures for pyrroloazepine.thianaphthene, and carbostyril derivatives, we found that the cyclization with phosphorus pentoxide and methanesulfonic acid (PPMA: 1 :9 weight ratio) provided those heterocyclic 5.
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Cho et al. (1996) studied this question.