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%
Highly enantioselective cascade synthesis of spiropyrazolones
作者:Alex Zea、Andrea-Nekane R. Alba、Andrea Mazzanti、Albert Moyano、Ramon Rios
DOI:10.1039/c1ob05753g
日期:——
An efficient synthesis of spiropyrazolones based on organocatalysis is described. The reaction between pyrazolones, enolizable aldehydes and enals is catalyzed by secondary amine catalysts and affords the final spiro compounds bearing four contiguous chiral centers in good yields and excellent diastereo- and enantioselectivities.
Bisphosphine catalyzed sequential [3 + 2] cycloaddition and Michael addition of ynones with benzylidenepyrazolones <i>via</i> dual α′,α′-C(sp<sup>3</sup>)–H bifunctionalization to construct cyclopentanone-fused spiro-pyrazolones
作者:Jiayong Zhang、Zhiwei Miao
DOI:10.1039/c8ob02675k
日期:——
A bisphosphine-catalyzed sequential [3 + 2] cycloaddition and Michael addition reaction of ynones with benzylidenepyrazolones has been developed. Under the catalysis of DPPB [1,4-bis(diphenylphosphino)butane], the reaction proceeded smoothly to give spiro-[cyclopentanone] pyrazolone derivatives in moderate to good yields with good diastereoselectivities via sequential dual α′,α′-C(sp3)–H bifunctionalization
Optically Active 4-Substituted 5-Nitropentan-2-ones: Valuable Chiral Building Blocks for the Stereocontrolled Construction of Spiro-Pyrazolone Scaffolds with Five Contiguous Stereogenic Centers
作者:Jiao Sun、Cuiping Jiang、Zhenghong Zhou
DOI:10.1002/ejoc.201501449
日期:2016.2
The application of readily available opticallyactive4-substituted5-nitropentan-2-ones as chiralbuildingblocks in the stereocontrolledconstruction of spiro-pyrazolonescaffolds was investigated. In the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (1 equiv.) opticallyactive4-substituted 5-nitropentan-4-ones exhibited excellent chiral inducing abilities in the diastereoselective cascade Michael/aldol
A new and efficient one-pot strategy combining catalyst-free synthesis and iodinecatalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones. This approach affords products in moderate to high yields (up to 96%) with excellent diastereoselectivities (up to >25 : 1 dr). The reaction is simple to carry out and is metal-free.