Diels−Alder Cycloaddition Strategy for Kinetic Resolution of Chiral Pyrazolidinones
作者:Mukund P. Sibi、Keisuke Kawashima、Levi M. Stanley
DOI:10.1021/ol901504p
日期:2009.9.3
A rare example of the application of a catalytic, enantioselective Diels−Aldercycloaddition to affect a kinetic resolution has been developed. Chiral pyrazolidinones are resolved with high selectivity through a process that utilizes a relay of stereochemical information from a permanent chiral center to a fluxional chiral center to enhance the inherent selectivity of the chiral Lewis acid catalyst
The development of highly active acyclic chiral hydrazides for asymmetric iminium ion organocatalysis
作者:Eoin Gould、Tomas Lebl、Alexandra M. Z. Slawin、Mark Reid、Tony Davies、Andrew D. Smith
DOI:10.1039/c3ob41719k
日期:——
Double asymmetric induction has been employed as a tool to optimise pyrazolidinone-derived organocatalysts for the asymmetric iminiumion catalysed Diels–Alder reaction. Mechanistic studies revealed a superior hydrazide catalyst deriving from methanolysis of the chiral pyrazolidinone precursor. This catalyst displays unusually high endo diastereoselectivity and good enantioselectivity with a range
A silver halide color photographic material comprising (1) at least one coupler and (2) at least one compound represented by formula (I) ##STR1## wherein EAG represents a group capable of accepting an electron from a reducing substance; R.sup.1 and R.sup.2 each represents a chemical bond or a divalent substituent, or R.sup.1 and R.sup.2 are linked together to form a cyclic structure when linked with (Time).sub.t PUG; or R.sup.1 and R.sup.2 each represents a substituent, or R.sup.1 and R.sup.2 are linked together to form a cyclic structure when not linked with (Time).sub.t PUG; Time represents a group capable of releasing PUG, which is released by the cleavage of the single bond between the oxygen atom and the nitrogen atom in the compound; t represents 0 or 1; PUG represents a photographically useful group; and the dotted lines mean that at least one of them forms a chemical bond, and a method for forming an image using the material.
Kinetic Resolutions of Azomethine Imines via Copper-Catalyzed [3 + 2] Cycloadditions
作者:Andrés Suárez、C. Wade Downey、Gregory C. Fu
DOI:10.1021/ja052876h
日期:2005.8.1
An effective method has been developed for the kinetic resolution of racemic azomethine imines via [3 + 2] cycloadditions with alkynes catalyzed by a chiral copper complex. Efficient kinetic resolution is observed for a variety of N1 and C5 substituents on the dipole, thereby furnishing a wide array of useful enantioenriched azomethine imines, which can readily be transformed into monocyclic and bicyclic pyrazolidinones.