(Mac‐SILC) in the pores of silica gel with the aid of an ionic liquid – 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide. The heterogenized organocatalyst was utilized for the enantioselectiveDiels–Alder reaction of cyclopentadiene and cinnamaldehyde, recovered by simple filtration and subsequent evacuation, and repeatedly used up to six times in 81% average chemical yield, 87% ee for endo‐
Structural effects in pyrazolidinone-mediated organocatalytic Diels–Alder reactions
作者:Eoin Gould、Tomas Lebl、Alexandra M.Z. Slawin、Mark Reid、Andrew D. Smith
DOI:10.1016/j.tet.2010.09.021
日期:2010.11
promoted Diels–Alderreactions evaluated. Systematic variation of the C(5)- and N(2)-substituents indicates that the incorporation of an electron withdrawing substitutent at N(2) and either a Ph or CF3 substitution at C(5) results in optimal catalytic activity. The diastereoisomeric resolution of a model C(5)-Ph substituted pyrazolidinone and its ability to impart modest levels of asymmetric induction
Aqueous Enantioselective Organocatalytic Diels−Alder Reactions Employing Hydrazide Catalysts. A New Scaffold for Organic Acceleration
作者:Mathieu Lemay、William W. Ogilvie
DOI:10.1021/ol051476w
日期:2005.9.1
[reaction: see text] Cyclic hydrazides function as asymmetric organocatalysts in aqueous Diels-Alderreactions. The hydrazide is employed as the catalytic machinery in a compact camphor-derived framework that imparts facial selectivity to the cycloadditions. Kinetic evidence suggests the reaction involves rapid iminium formation.
Design of a Conformationally Rigid Hydrazide Organic Catalyst
作者:Mathieu Lemay、Livia Aumand、William W. Ogilvie
DOI:10.1002/adsc.200600268
日期:2007.2.5
Conformational control was utilized to design a hydrazide organocatalyst for asymmetric Diels–Alder reactions, thus introducing a new aspect to organocatalysis. Diastereoselectivities and enantioselectivities of up to 96 % were achieved by the application of the rigidified catalyst. The first crystal structure of a key iminium intermediate in an organocatalyzed process is also provided.
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