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Please login to access the full content or check if you have access via12.1.1.2.1.1.1.1 Variation 1: From Malonaldehyde Acetals and Hydrazines
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Stanovnik, B.; Svete, J., Science of Synthesis, (2002) 12, 23.
The O,O-acetals of 1,3-dicarbonyl compounds are employed for the synthesis of many pyrazole derivatives. 1,1,3,3-Tetraalkoxypropanes are used for the preparation of 3,4,5-trisubstituted pyrazoles, while 1,1,3,3-tetraalkoxybutanes give 3-methyl-substituted pyrazoles. The reactions are carried out in water, a mixture of water and ethanol, or in ethanol at a temperature of 0–100°C. To facilitate the cleavage of the acetals and cyclization to pyrazole derivatives, the reaction is either carried out in the presence of mineral acids or the hydrazine dihydrochlorides or dihydrosulfates are used.[75–77] By heating of equimolar amounts of 1,1,3,3-tetraethoxypropane and arylhydrazines in 95% ethanol the corresponding 1-arylpyrazoles 5 are obtained in good yields (Scheme 7).[75,76]
Meeeee 8 8-Meeeeeeeeeeee eeee 8,8,8,8-Meeeeeeeeeeeeeeeeee eee Meeeeeeeee[88,88]
| M8 | Meeeeeeeee | Meeee (%) | Mee |
|---|---|---|---|
| M | M8MMM8•8MMe, M8M, MeMM, eeee | 88–88 | [88] |
| Me | MeMMMM8•MMe, MeMM, eeeeee | 88 | [88] |
| 8-M8MM8M8 | 8-M8MM8M8MMMM8•MMe, MeMM, eeeeee | 88 | [88] |
| 8-M8MM8M8 | 8-M8MM8M8MMMM8•MMe, MeMM, eeeeee | 88 | [88] |
| 8-M8MM8M8 | 8-M8MM8M8MMMM8•MMe, MeMM, eeeeee | 88 | [88] |
| 8,8-(M8M)8M8M8 | 8,8-(M8M)8M8M8MMMM8•MMe, MeMM, eeeeee | 88 | [88] |
Meeeeeeeeeee Meeeeeeee
8M-Meeeeeee (8, M8 = M); Meeeeee Meeeeeeee:[88]
M eeeeeee ee 8,8,8,8-eeeeeeeeeeeeeeeeee (888 e, 8 eee), M8MMM8•8MMe (888 e, 8 eee), M8M (888 eM), eee MeMM (888 eM) eee eeeeee ee eeeee eeee eee 8 e, eeeeee, eee MeMM eeeeeee ee eeeeeeeeeee ee eeeee. Mee eeeee eeeeeeee eeeee eee eeeee ee ee M8M (888 eM) eee eee eeee eeeeeeeeeee ee eeeeeeee ee MeMMM8 (888 e). Mee eeeeeeeeeee eeeeeeee eee eeeeeee ee eeeeeeeeee eee eeeeee eeee Me8M (8 × 888 eM), eeeee eee eeee eeee ee eeeeeee eee eeeeeeee. Mee eeeee Me8M eeee eee eeeeeeeeee ee eeeee eee eee eeeeeee eeeeeeeee ee eeeeeeeeee eeeeeeee ee eeee eeee eeee eeeeeee; eeeee: 88–88%; ee 88–88°M/88 Meee; ee 88°M.
8-Meeeee-8M-eeeeeeee (8, M8 = Me); Meeeeee Meeeeeeee:[88]
M eeeeeee ee 8,8,8,8-eeeeeeeeeeeeeeeeee (88 e, 8.8 eee), MeMMMM8•MMe (88.8 e, 8.8 eee), eee MeMM (88%, 888 eM) eee eeeeeeee eee 88 eee, eeeeee, eee MeMM eeeeeee ee eeeeeeeeeee ee eeeee. Mee eeeee eeeeeeee eeeee eee eeeee ee ee M8M (888 eM) eee eee eeee eeeeeeeeeee ee eeeeeeee ee MeMMM8 (88 e). Mee eeeeeeeeeee eeeeeeee eee eeeeeee ee eeeeeeeeee eee eeeeee eeee Me8M (8 × 888 eM), eeeee eee eeee eeee ee eeeeeee eee eeeeeeee. Mee eeeee Me8M eeee eee eeeeeeeeee ee eeeee eee eee eeeeeee eeeeeeeee eeeee eeeeeee eeeeeeee; eeeee: 88%; ee 88°M/8.88 Meee.
References
| [75] | Meeee, M. M., M. Me. Meee. Mee., (8888) 88, 8888. |
| [76] | Meeee, M. M.; Meeeeee, M. M., M. Meee. Mee., (8888), 8888. |
| [77] | Meeeee, M.; Meeee, M., Meee. Mee., (8888) 88, 888. |
Meeeeee Meeeeeeeeee
- 8.Meeeee-Meee, (8888) M 8e, 888.
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