The present invention provides an organocatalyst of formula (I),
wherein R
1
is —H, —OH, —O—Si(R
4
)(R
5
)(R
6
) or C
1-6
alkoxy, in which R
4
, R
5
and R
6
are identical or different and independently selected from the group consisting of C
1-6
alkyl, phenyl and phenyl substituted with C
1-6
alkyl; R
2
is —OH or ═O; X
1
is one selected from the group consisting of —NH—, —S— and
X
2
is one selected from the group consisting of —C(═O)—, —CH
2
— and
and X
1
is different from X
2
. The high yield and enantioselectivity of an addition reaction are obtained by using the organocatalyst of the present invention.
α,β-dipeptides as chiralorganocatalysts in the asymmetricMichaeladditionreaction between enolizable aldehydes and N-arylmaleimides or nitroolefins is described. With N-arylmaleimides as substrates, the best results were achieved with dipeptide 2 as a catalyst in the presence of aq. NaOH. Whereas dipeptides 4 and 6 in conjunction with 4-dimethylaminopyridine (DMAP) and thiourea as a hydrogen bond
9‐amino‐9‐deoxy‐epi‐quinine were then used in the same reaction with different substrates, leading to the desired products in high yield and ee, as well as in three other reactions operating with different mechanism. An investigation of the recyclability of the polystyrene‐ and poly(ethylene glycol)‐supported systems showed that these could be recovered and recycled with no loss of stereochemical activity but with a
Asymmetric Conjugate Addition of α,α-Disubstituted Aldehydes to Nitroalkenes Organocatalyzed by Chiral Monosalicylamides from trans-Cyclohexane-1,2-Diamines
Primary amine-salicylamides derivedfrom chiral trans-cyclohexane-1,2-diamines are used as organocatalysts for the enantioselective conjugateaddition of α,α-disubstituted aldehydes to arylated and heteroarylated nitroalkenes. The reaction is performed in the presence of 4-dimethylaminopyridine as an additive in dichloromethane as a solvent at room temperature. The corresponding enantioenriched γ-nitroaldehydes
Highly efficient asymmetric organocatalytic Michael addition of α,α-disubstituted aldehydes to nitroolefins under solvent-free conditions
作者:Junpeng He、Qiankun Chen、Bukuo Ni
DOI:10.1016/j.tetlet.2014.03.107
日期:2014.5
with benzoic acid has been found to be an effective organocatalyst for Michaeladdition of α,α-disubstituted aldehydes with nitroolefins. The reaction provided the desired Michael products possessing all-carbon quaternary center with high yields (76–98%) and high levels of enantioselectivities (up to 97% ee) under solvent-free reaction conditions. The procedure presented is simple and makes this method