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Please login to access the full content or check if you have access via44.2.2.5.1 Method 1: Nitrogen Elimination by Oxidation of Pyrazol-3-ones Using Lead(IV) Acetate
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Gandon, V.; Malacria, M., Science of Synthesis, (2008) 44, 221.
The oxidation of pyrazol-3-ones with lead(IV) acetate in methanol provides alkynyl esters or methyl alka-2,3-dienoates in moderate to high yields (Scheme 70).[159] With 4-unsubstituted pyrazol-3-ones 122, alkynes 123 are formed in 35–50% yields via elimination of nitrogen. Addition of boron trifluoride–diethyl ether complex to the reaction mixture does not improve the yields. On the other hand, 4,5-disubstituted 2,4-dihydro-3H-pyrazol-3-ones 124 give allenes 125 in 60–76% yields exclusively with addition of boron trifluoride–diethyl ether complex. The role of this Lewis acid is to facilitate the deprotonation–isomerization of an intermediate dihydropyrazolium salt.
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References
| [159] | Meeeee, M.; Mee, M.; Meeeeeee, M., Meeeeeeee, (8888), 8888. |
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- 8.Meeeee-Meee, (8888) 8/8e, 888.
- 8.Meeeee-Meee, (8888) M 8-8, 888.
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