H-Bond-Directing Organocatalyst for Enantioselective [4 + 2] Cycloadditions via Dienamine Catalysis
作者:Shoulei Wang、Carles Rodriguez-Escrich、Miquel A. Pericàs
DOI:10.1021/acs.orglett.5b03575
日期:2016.2.5
regio- and stereoselective [4 + 2] cycloaddition reaction to generate tetrahydropyranopyrazole frameworks has been developed. To this end, a dienamine-based catalytic strategy that relies on the H-bond-directing effect of the hydroxy group of a dinaphthylprolinol-type aminocatalyst has been used. This enables the synthesis of multifunctionalized heterocyclic derivatives with threecontiguous stereocenters
Organophosphane-Catalyzed Direct β-Acylation of 4-Arylidene Pyrazolones and 5-Arylidene Thiazolones with Acyl Chlorides
作者:Pankaj V. Khairnar、Yin-Hsiang Su、Yung-Chang Chen、Athukuri Edukondalu、Yi-Ru Chen、Wenwei Lin
DOI:10.1021/acs.orglett.0c02408
日期:2020.9.4
An efficient method for the direct β-acylation of arylidene pyrazolones and thiazolones with acyl chlorides in the presence of a base catalyzed by organophosphanes is reported. A variety of functionalized 4-arylidene pyrazolone and 5-arylidene thiazolonederivatives were prepared under metal-free and mild conditions via a tandem phospha-Michael addition/O-acylation/intramolecular cyclization/rearrangement
amine–thioureas are effective catalysts for the first diastereo- and enantioselectiveepoxidation of unsaturated pyrazolones. The trans- or cis-spiroepoxides are preferentially obtained in good yield and high to excellent enantioselectivityusing an appropriate organocatalyst and tert-butyl hydroperoxide as the oxidant. The epoxidation appears applicable to highly challenging β,β′-substituted unsaturated