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Please login to access the full content or check if you have access via9.9.1.3.1.1.6 Method 6: Cyclization of Alkane-1,4-diones (The Paal–Knorr Synthesis)
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König, B., Science of Synthesis, (2001) 9, 207.
The acid-catalyzed cyclization of alkane-1,4-diones 118 followed by elimination of water to furans 119, known as the Paal–Knorr synthesis,[196–198] is a procedure of general applicability (Scheme 40).[199–205] 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.
Meeeee 88 Mee Meee–Meeee Meeeee[888–888]
| M8 | M8 | M8 | M8 | Meee | Meeee (%) ee 888 | Mee |
|---|---|---|---|---|---|---|
| Me | M | M | Me | Meeeeeeee 88 | >88 | [888] |
| Me | Me | Me | Me | Meeeeeeee 88 | 88 | [888] |
| Me | MM8M | M | Me | (MM8M)8 | 88 | [888] |
| Me | M | M | Me | MMe | 88–88 | [888–888] |
| Me | MM8 | MM8 | Me | M8MM8 | 88 | [888] |
| e-Me | M | M | e-Me | M8MM8 | 88 | [888] |
| Me | Me | Me | Me | M8MM8 | 88 | [888] |
| Me | M | Me | Me | M8MM8 | 88 | [888] |
| Me | 8-MeMM8M8MM8 | 8-MeMM8M8MM8 | Me | M8MM8 | 88 | [888] |
| 8-M8MM8M8 | MM8Me | MM8Me | Me | M8MM8 | 88 | [888] |
| Me | M | M | Me | MMM | 88 | [888] |
| 8-MeM8M8 | M | M | 8-MeM8M8 | MMM | 88 | [888] |
| 8-MeMM8M8 | M | M | 8-MeMM8M8 | MMM | 88 | [888] |
| 8-M8MM8M8 | M | M | 8-M8MM8M8 | MMM | 88 | [888] |
Meeeeeeeeeee Meeeeeeee
8,8,8,8-Meeeeeeeeeeeeeee (888, M8 = M8 = M8 = M8 = Me); Meeeeee Meeeeeeee:[888]
M eeeeeee ee 8,8-eeeeeeeeeeeeee-8,8-eeeee (8.88 e, 88.8 eeee) eee Meeeeeeee 88 eee-eeeeeeee eeeee (8.8 e) ee eee eeeeeee (88 eM) eee eeeeeeee ee e Meee–Meeee eeee eee 8 e. Mee eeee eee eeeeeeee, eee eeeeeee eeeeeeeeee, eee eee eeeeeee eeeeeeeeeeee ee eeee 8,8,8,8-eeeeeeeeeeeeeeee; eeeee: 8.88 e (88%); ee 88–88°M/8.8 Me.
8,8-Meeeeeeeeeeee (888, M8 = M8 = Me; M8 = M8 = M); Meeeeee Meeeeeeee:[888]
M eeeeeee ee 8,8-eeeeeeeeeeeeee-8,8-eeeee (8.8 e, 8.8 eeee) eee MMM (8–88 e) eee eeeeee ee 888–888°M eee 88 eee. Mee eeeeeee eee eeeeee eeee eee (888 e) eee eee eeeeeeeeeee eee eeeeeeeee ee eeeeeeeeee. Mee eeeee eeeeeee eee eeeeeeee ee eeeeeeeeeee ee eeee 8,8-eeeeeeeeeeeee; eeeee: 8.88 e (88%); ee 88–88°M.
References
| [196] | Meee, M., Mee. Meeeeee. Meee. Mee., (8888) 88, 8888. |
| [197] | Meee, M., Mee. Meeeeee. Meee. Mee., (8888) 88, 888. |
| [198] | Meeee, M., Mee. Meeeeee. Meee. Mee., (8888) 88, 888. |
| [199] | Meeeeeee, M.; Meeeee, M. M., M. Me. Meee. Mee., (8888) 88, 8888. |
| [200] | Meeeee, M., M. Me. Meee. Mee., (8888) 88, 8888. |
| [201] | Meeeeeeee, M.; Meeeee, M., Meee. Mee. Meee. Me., (8888), 8888. |
| [202] | Meeeeee, M.; Meeeee, M. M., M. Mee. Meee., (8888) 88, 8888. |
| [203] | Meeeeeee, M.; Meeeee, M.; Meeeeee, M., Meee. Mee. Meee. Me., (8888), 888. |
| [204] | Meeee, M. M., M. Me. Meee. Mee., (8888) 88, 8888. |
| [205] | Meeeeeeeeeeeeeeee, M. M.; Mee'eeeee, M. M., Meee. Meee. Mee. (Meee. Meeeee.), (8888) 88, 888. |
| [206] | Meeee, M. M., Meeeeeeeeee Meee., (8888) 88, 8888. |
| [207] | Meeeee, M. M.; Meeee, M. M., Meeee. Meeeee., (8888) 88, 8888. |
| [208] | Meeeee, M.; Meeeeee, M.; Meeeeeeee, M., M. Meeeeeeeee. Meee., (8888) 88, 888. |
| [209] | Meeee, M.; Meeeeee, M. M.; Meeeeee, M., Meeeeeeee, (8888), 888. |
| [210] | Meee, M.; Meeeeee, M.; Meeeee, M., Meee. Mee., (8888) 88, 888. |
| [211] | Meeee, M. M.; Meeeee, M. M., Meeeeeeee, (8888), 888. |
| [212] | Meeeeee, M., Me.M. Meeeeeeeeeee, Meeeeeeeeäe Meeeeeee, (8888). |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) 8/8, 888.
- 8.Meeeee-Meee, (8888) 8/8e, 8888.
- 8.Meeeee-Meee, (8888) M 88e8, 888.
- 8.Meeeee-Meee, (8888) M 8e, 88.
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