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Please login to access the full content or check if you have access via Method 6: Cyclization of Alkane-1,4-diones (The Paal–Knorr Synthesis)

DOI: 10.1055/sos-SD-009-00244

König, B.Science of Synthesis, (20019207.

The acid-catalyzed cyclization of alkane-1,4-diones 118 followed by elimination of water to furans 119, known as the PaalKnorr synthesis,[‌196‌‌198‌] is a procedure of general applicability (Scheme 40).[‌199‌‌205‌] Bis(epoxides) have been used as starting materials.[‌206‌] A variety of catalysts have been used: sulfuric acid,[‌207‌,‌208‌] hydrochloric acid, polyphosphoric acid,[‌209‌] 4-toluenesulfonic acid, oxalic acid,[‌210‌] ion-exchange resins, such as Amberlyst 15,[‌211‌] and acetic anhydride/zinc bromide.

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