Efficient One-Pot Synthesis of β-Unsaturated Isoxazol-5-ones and Pyrazol-5-ones Under Ultrasonic Irradiation
摘要:
4-Arylmethylidene-3-isopropylisoxazol-5-ones and 4-arylmethylidene-1-phenyl-3-isopropylpyrazol-5-ones have been prepared from the reactions of hydroxylamine and phenylhydrazine with methyl 4-methyl-3-oxovalerate and aromatic aldehydes in an aqueous medium at room temperature in the presence of pyridine under ultrasonic irradiation. The simple and facile method produced products in good yields.Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications (R) to view the free supplemental file.
A chiral N-heterocyclic carbene (NHC)-catalyzed [4 + 2] annulation of γ-chloroenals and α-arylidene pyrazolinones was developed in the absence of expensive oxidants. The reaction proceeds smoothly via a vinyl enolate intermediate to afford spirocyclohexane pyrazolones in moderate to good yield (up to 86%) with high diastereoselectivities (up to 15:1 dr) and excellent enantioselectivities (up to >99%
Enantioselective Synthesis of Spiropyrazolone-Fused Cyclopenta[<i>c</i>]chromen-4-ones Bearing Five Contiguous Stereocenters via (3+2) Cycloaddition
作者:Pankaj V. Khairnar、Yin-Hsiang Su、Athukuri Edukondalu、Wenwei Lin
DOI:10.1021/acs.joc.1c01215
日期:2021.9.3
An enantioselectivesynthesis of spiropyrazolone-fused cyclopenta[c]chromen-4-ones is demonstrated via a (3+2) cycloaddition reaction. The reactions of 3-homoacylcoumarins and α,β-unsaturated pyrazolones in the presence of the cinchona-alkaloid derived hydrogen-bonding catalyst provide aforementioned spiropyrazolone-chromenone adducts bearing five contiguous stereocenters, of which one is the spiro
通过 (3+2) 环加成反应证明了螺吡唑酮稠合的 cyclopenta[ c ]chromen-4-ones的对映选择性合成。3-高酰基香豆素与α,β-不饱和吡唑啉酮在金鸡纳生物碱衍生的氢键催化剂存在下反应,得到上述螺吡唑酮-色烯酮加合物,其具有五个连续的立体中心,其中一个是螺环全碳四元立体中心。产率(高达 98%),具有良好到出色的立体选择性(>25:1 dr 和高达 99% ee)。这种一锅法也可以在具有类似功效的克级规模上得到实际证明。
The catalytic asymmetric synthesis of CF<sub>3</sub>-containing spiro-oxindole–pyrrolidine–pyrazolone compounds through squaramide-catalyzed 1,3-dipolar cycloaddition
important compounds were synthesized through the organocatalytic 1,3-dipolar cycloadditionreaction. In the presence of a cinchonine-derived squaramide catalyst, the cycloaddition of N-2,2,2-trifluoroethylisatin ketimines with α,β-unsaturated pyrazolones gave a spiro-pyrrolidine-linked oxindole and pyrazolone compound bearing four consecutive stereocenters and two vicinal spiroquaternary chiral centers
A DMAP-catalyzed [4 + 2] annulation of α-substituted allenoates with unsaturated pyrazolones has been achieved in dichloromethane at 40 °C, providing multisubstituted tetrahydropyrano [2,3-c]pyrazoles in good to excellent yields with moderate to good Z/E ratios. The allenoates worked as two-carbon synthons in the reaction.