Enantioselective Synthesis of Coumarin Derivatives by PYBOX-DIPH-Zn(II) Complex Catalyzed Michael Reaction
作者:Sumit K. Ray、Pradeep K. Singh、Nagaraju Molleti、Vinod K. Singh
DOI:10.1021/jo301513x
日期:2012.10.5
A potential pharmacologically active chiral 3-substituted 4-hydroxy-2-oxo-2H-chromene skeleton has been synthesized by enantioselectiveMichael addition catalyzed by PYBOX-DIPH-Zn(OTf)2 complex. The methodology has successfully been employed in the synthesis of (R)-Warfarin and another related compounds.
Enantioselective synthesis of 3,4-dihydropyran derivatives via a Michael addition reaction catalysed by chiral pybox–diph–Zn(ii) complex
作者:Sumit K. Ray、Subhrajit Rout、Vinod K. Singh
DOI:10.1039/c3ob40246k
日期:——
An enantioselective Michael addition of cyclic 1,3-dicarbonyls to 2-enoylpyridine N-oxides catalyzed by a chiral pyboxâdiphâZn(II) complex has been developed. The corresponding Michael adducts have been obtained in high yields with up to >99% ee. The Michael adduct has been transformed to biologically active 2,4-disubstituted hexahydroquinoline. A plausible transition-state model has been proposed to explain the stereochemical outcome of the reaction.
Asymmetric Direct Vinylogous Michael Addition to 2-Enoylpyridine <i>N</i>-Oxides Catalyzed by Bifunctional Thio-Urea
作者:Subhrajit Rout、Sumit K. Ray、Rajshekhar A. Unhale、Vinod K. Singh
DOI:10.1021/ol5025794
日期:2014.11.7
Catalytic enantioselectivedirectvinylogousMichaeladdition of α,α-dicyanoalkenes to 2-enoylpyridine N-oxides with a bifunctional organocatalyst is described. The methodology offers an efficient way to install an asymmetric carbon–carbon bond at the γ-position of α,α-dicyanoalkenes in excellent regio-, diastereo-, and enantioselectivity. Further, application in desymmetrization of achiral α,α-dicyanoalkene
Enantioselective Friedel−Crafts Alkylation of Pyrroles Catalyzed by PYBOX-DIPH-Zn(II) Complexes
作者:Pradeep K. Singh、Vinod K. Singh
DOI:10.1021/ol902360b
日期:2010.1.1
A highly enantioselectiveFriedel−Craftsalkylation of pyrroles with 2-enoylpyridine N-oxides catalyzed by chiral PYBOX-DIPH-Zn(II) complexes has been developed. The catalyst offers substantial substrate scope and furnished alkylated pyrroles in excellent yields (up to 99%) and enantioselectivities (up to >99% ee).