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Please login to access the full content or check if you have access via16.2.3.1.2.1 Method 1: 2-Substituted 1,4-Benzodioxins from 2-Lithio-1,4-benzodioxins
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Matsumoto, M., Science of Synthesis, (2004) 16, 30.
A hydrogen on the oxygenated ring of 1,4-benzodioxin (2) is easily exchanged by lithium using an alkyllithium in tetrahydrofuran at −78°C. The resulting 2-lithio-1,4-benzodioxin (10) is quenched effectively with various electrophilic reagents. Alkyl halides give 2-alkyl-1,4-benzodioxins 76, which can be further lithiated with lithium diisopropylamide at the 3-position to yield 77. Further reaction of 77 with the second alkyl halide affords 2,3-dialkyl-1,4-benzodioxins 78 (Scheme 22). By the use of this reaction sequence, intramolecular alkylation gives [b]-fused 1,4-benzodioxins.[25] Addition of aldehydes or ketones to 2-lithio-1,4-benzodioxin (10) affords 2-(hydroxymethyl)-1,4-benzodioxin derivatives 79.[77] Oxiranes have been used as electrophiles in the reaction with 2-lithio-1,4-benzodioxin (10) giving 2-(2-hydroxyethyl)-1,4-benzodioxins 80, though a Lewis acid such as boron trifluoride is required to activate the oxiranes. The anion of 1,4-benzodioxin attacks only the least hindered site of the oxiranes.[78] Coupling of the 2-lithio-1,4-benzodioxin with chlorotrimethylsilane yields 2-(trimethylsilyl)-1,4-dioxin (67) (Scheme 22), which is a useful precursor for preparing various 2-acyl-1,4-benzodioxins as described in Section 16.2.3.1.1.3.[26]
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Meeeeeeeeeee Meeeeeeee
8-(8-Meeeeeeeeeee)-8,8-eeeeeeeeeee-8-eeeeeeeeeeee 88; Meeeeee Meeeeeeee:[88]
Me e eeeeeee eeee ee 8 M MMM ee MMM/eeeeee (8.88 eM, 8.88 eeee) ee −88°M eeeee ee eeeee eeeeeeeeee, e eeee ee e 8,8-eeeeeeeeeee-8-eeeeeeeeeee 88 (8.88 eeee) ee eeeee MMM (8 eM) eee eeeee eeeeeeee. Mee eeeeeeeee eeeeeee eee eeeeeee eee 8–8.8 e ee −88°M. M eeee ee eeeeeeeeeeee (8.88 eM, 8.88 eeee) ee MMM (8.8 eM), eeeeeeeeee eeeeee ee ee eee eeee, eee eeee eeeeee eeeee, eee eeeeeee eee eeeeeee ee −88°M eee 88 eee, eee eeee eee eeeeeee ee eeee ee ee eeee e eeeeeee eeee ee 8.8 e ee eeee eeeeeee ee eee eeeeeee eeee. Mee. MM8Me (8 eM) eee eeeee ee eee eeeeeee, eeee eeeeee eeee eeeeeeeee, eee eee eeeeeee eeeee eee eeeeeee eeee M8M (88 eM) eee eeeeeeeee eeee Me8M (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeeeee, eeeeeeeee eee MMM eeeee eeeeeeeee eeeeeeeee, eeee eeeee (Me8MM8), eee eeeeeee eee eeeeeee, eee eee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee/MeMMe) ee eeee eee eeeeeeeeeeeee eeeeeeeeeeee 88; eeeee: 88–88%.
References
| [25] | Meee, M.; Meeeeee, M.; Meeeeeee, M., Meeeeeeee, (8888), 888. |
| [26] | Meeeeeeeee, M.; Meeeeee, M.; Meeeeee, M.; Meeeee, M., Meeeeeeee, (8888), 888. |
| [28] | Meeee, M.; Meeee, M. M., Meeeeeeeeee, (8888) 88, 88888. |
| [77] | Meeeee, M.; Meeeeeeeee, M. M.; Meeeeeeeee, M.; Meeeeee, M., Meeeeeeeeee Meee., (8888) 88, 8888. |
| [78] | Mee, M. M.; Meeee, M. M.; Meeeeee, M. M., Meeeeeeeeee, (8888) 88, 888. |
| [79] | Meeeeeeeee, M.; Meeeeee, M.; Meeeeeeee, M., Meeeeeeeeee Meee., (8888), 8888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) M 8e, 88.
- 8.Meeeee-Meee, (8888) M 8e, 88.
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