Enantioselective synthesis of functionalized fluorinated dihydropyrano [2,3-c]pyrazoles catalyzed by a simple bifunctional diaminocyclohexane-thiourea
作者:Hong-Fei Zhang、Zheng-Qing Ye、Gang Zhao
DOI:10.1016/j.cclet.2014.01.034
日期:2014.4
Abstract Enantioselectivesynthesis of functionalized fluorinated dihydropyrano[2,3-c]pyrazoles has been achieved via a diaminocyclohexane-thiourea catalyzed cascade Michael addition and Thorpe-Ziegler type cyclization in high yields (up to 98%) with moderate to good enantioselectivity (up to 90% ee ).
Organocatalyzed asymmetric tandem Michael-cyclization reaction of 4-benzylidene-3-methylpyrazol-5-ones and malononitrile: stereocontrolled construction of pyrano[2,3-c]pyrazole scaffold
作者:H.-X. Wang、L.-L. Wu、Y.-M. Wang、Z.-H. Zhou
DOI:10.1039/c5ra04356e
日期:——
An efficient approach for the stereocontrolled construction of pyrano[2,3-c]pyrazole scaffold has been developed. Under the catalysis of a bifunctionalsquaramide derived from (1R,2R)-1,2-diphenylethane-1,2-diamine, the asymmetric tandem Michael addition/cyclization reaction of 4-benzylidenepyrazol-5(4H)-ones and malononitrile proceeded efficiently to furnish the desired pyrano[2,3-c]pyrazoles in satisfactory
开发了一种有效的立体控制吡喃并[2,3- c ]吡唑支架的方法。在衍生自(1 R,2 R)-1,2-二苯乙烷-1,2-二胺的双官能方酰胺的催化下,4-苄叉基吡唑-5(4 H)-的不对称串联迈克尔加成/环化反应与丙二腈有效地进行,以令人满意的产率提供了所需的吡喃并[2,3- c ]吡唑类,并具有高水平的对映体选择性(至多99%ee)。
Mechanistic Insights into Annulation of Arylidene‐Δ
<sup>2</sup>
‐Pyrrolin‐4‐Ones by Cinchona Squaramide‐Based Organocatalysts
AbstractArylidene‐Δ2‐pyrrolin‐4‐ones undergo organocatalyzed annulation with malononitrile, furnishing dihydropyrano[3,2‐b]pyrroles (18 examples, 0–77% ee in dichloromethane, 11–44% ee in methanol). The products could be enantiomerically enriched by trituration (11 examples, 95–99% ee). Enantioselectivity was dependent on the nature of the substrate and the conformation of the catalyst, which in turn was solvent‐controlled. The reaction mechanism, which included two pseudo‐enantiomeric organocatalyst conformations, was investigated by experimental and quantum chemical methods. The reaction mechanism consists of Michael addition reaction step followed by 6‐exo‐dig annulation, which was found to be the rate determining step. Additionally, it was identified that the preferred reaction pathway follows the model originally proposed by Pápai et al.magnified image