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Please login to access the full content or check if you have access via9.9.2.3.3 Method 3: Synthesis from 3,6-Dihydro-1,2-dioxins
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König, B., Science of Synthesis, (2001) 9, 230.
3,6-Dihydro-1,2-dioxins 218, which can be obtained by Diels–Alder addition of photochemically generated singlet oxygen to electron-rich cyclic or acyclic 1,3-dienes,[375] are suitable starting materials for the synthesis of alkyl- and arylfurans 219 (Scheme 75). Several methods have been developed for their ring-contraction reaction with elimination of water.[376,377] The reaction can be achieved thermally[376] or with acid catalysis,[378] but base catalysis has been used in most cases. Potassium hydroxide,[379] lithium tert-butoxide,[380,728] potassium tert-butoxide,[381] and lithium diisopropylamide[382] have been employed as bases. To avoid side reactions the reaction conditions must be controlled carefully. Elimination of water from the intermediate dihydrofuranol also requires mild conditions. Good yields of the ring-contraction reactions have been obtained in the presence of iron(II) sulfate[377,383,384] or cobalt(II) tetraphenylporphyrin,[376,385] while the irradiation of 1:1 complexes of dihydro-1,2-dioxins 218 and tetracyanoethene gave furans in only moderate yields.[727]
Meeeee 88 Meeeeeeee ee Meeeee eeee 8,8-Meeeeee-8,8-eeeeeee[888]
| M8 | M8 | M8 | M8 | Meeeeeeeeee | Meeee (%) ee 888 | Mee |
|---|---|---|---|---|---|---|
| M | Me | M | M | M | 88 | [888] |
| M | e-Me | M | M | M | 88 | [888] |
| M | 8-MM-8-Me-eeeeee | M | M | M | 88 | [888] |
| Me | M | M | Me | M | eeeee | [888] |
| (MM8)8MM8 | M | M | (MM8)8MM8 | M | 88 | [888] |
| Me | M | M | Me | M | eeeee | [888] |
| Me | Me | M | M | M | eeeee | [888] |
e M: 8. MeMe-Me, MMM, −88°M; 8. eee. M8MM8 ee MMM ee MeMM eeee eeeee MeMMM8. M: MeMM8, M8M, MMM. M: 888°M, eeeeeee, 88 e.
Meeeeeeeeeee Meeeeeeee
8-(8-Meeee)-8-eeeeeeeeeeee-8-ee:[888]
M eeeeeee ee eeee(MM) eeeeeee eeeeeeeee (8.88 e, 8.8 eeee) ee M8M (88 eM) eee 8-(8-eeeeeee-8-eeeeeeeeeeee)-8,8-eeeeeee-8,8-eeeeee [eeeeeeee eeee 8-eeeeee-8-eeeeeeeeeeee-8-eee-8-ee (eeeeeeee) eee eeeeee ee e eeeeeeeeee eeeeeeeeeeeee eeeeeeee] (8.8 e, 8.8 eeee) ee MMM (88 eM) eee eeeeeee eee 8 e, eee eeeeeee eee eeeeeee ee eeeee, eee eeeeeee eee eeeeeee eeee M8M, eee eee eeeeeeeeeeee eeee eeeee eeee eeeeeee ee eeeeeeeeee. Mee eeeeeee eeeee eee eeeeeeeee eeee Me8M, eee eeeeeee eeeee eee eeeeee eeee M8M, eeeee, eee eee eeeeeee eee eeeeeeeeee ee eeeee. Meeeeeeeeeeeee ee eee eeeeeee eeee 8-(8-eeeee)-8-eeeeeeeeeeee-8-ee ee e eeeeeee eeeeee; eeeee: 8.88 e (88%).
References
| [375] | Meeeeeeeee, M. M.; Meeeeee, M. M.; Meeeee, M. M., Meeeeee Meeeee, MMM: Meee Meeee, (8888); Mee. MM, e 88. |
| [376] | Meeeee, M.; Meeeee, M.; Meeeee, M.; Meeeeeee, M.; Meeeee, M., M. Mee. Meee. (8888) 88, 8888. |
| [377] | Meee, M.; Mee, M.-M., M. Mee. Meee., (8888) 88, 888. |
| [378] | Mee, M.; Meeeeeeee, M., Meee. Mee. Meee. Me., (8888), 8888. |
| [379] | Meeee, M.; Meeeeeeee, M., Meee. Meee., (8888), 888. |
| [380] | Meeee, M.; Meeeeeeee, M., Meeeeeeeeee Meee., (8888), 888. |
| [381] | Meeeee, M.; Meeeee, M.; Meeeeeeee, M.; Meee, M., Meee. Meee., (8888), 8888. |
| [382] | Meeeeeeeee, M.; Meeeee, M. M., Meeee. Meeeee., (8888) 8, 888. |
| [383] | Meeeee, M. M.; Meee, M., M. Mee. Meee., (8888) 88, 8888. |
| [384] | Meeeeeeeöe, M.; Meeeee, M.; Mee Meeee, M.; Meeeeeee, M.; Meeee, M., Meee Meee. Meeee., Mee. M, (8888) 88, 88. |
| [385] | M\8Meee, M. M.; Meeee, M. M., M. Mee. Meee., (8888) 88, 8888. |
| [727] | Meeeeeeee, M.; Meeeeeeee, M.; Meeeeeeee, M.; Meeeeee, M., M. Meee. Mee., Meeeee Meeee. 8, (8888), 888. |
| [728] | Meeee, M.; Meeeeeeee, M.; Meeeeeeeeee Meee., (8888), 8888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) M 88-8, 8888.
- 8.Meeeee-Meee, (8888) M 88-8, 8888.
- 8.Meeeee-Meee, (8888) M 8e, 88.
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