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.
Enantioselective Michael addition of α,α-disubstituted aldehydes to nitroolefins catalyzed by a pyrrolidine-pyrazole
作者:Togapur Pavan Kumar、Kothapalli Haribabu
DOI:10.1016/j.tetasy.2014.06.009
日期:2014.8
efficient protocol for the asymmetric catalytic Michaeladditions of α,α-disubstitutedaldehydes to nitroolefins with a pyrrolidine-pyrazole is described. The desired products γ-nitrocarbonyl compounds possessing an all-carbon quaternary center, were obtained in good yields and with high levels of enantioselectivities undersolvent-free reaction conditions, employing benzoic acid as an additive.
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
Pyrrolidine–oxyimide catalyzed asymmetric Michael addition of α,α-disubstituted aldehydes to nitroolefins
作者:Togapur Pavan Kumar
DOI:10.1016/j.tetasy.2015.07.009
日期:2015.9
Organocatalyticenantioselective Michael addition of α,α-disubstituted aldehydes onto nitroolefins using pyrrolidine–oxyimide catalyst was reported. The reaction works effectively under neat conditions with 15 mol % of catalyst and 10 mol % of p-nitrobenzoic acid as an additive at 0 °C; this results in the formation of Michael adducts possessing an all-carbon quaternarycenter with good yields and
Calixarene-based highly efficient primary amine–thiourea organocatalysts for asymmetric Michael addition of aldehydes to nitrostyrenes
作者:Mustafa Durmaz、Abdulkadir Sirit
DOI:10.1080/10610278.2013.773331
日期:2013.5.1
The synthesis of calix[4]arene-based chiral bifunctional primary amine–thioureacatalysts has been described from p-tert-butylcalix[4]arene for the first time. The calix[4]arene-based catalysts were successfully applied to promote Michael addition of aldehydes with nitroalkenes affording preferentially the (R)- or (S)-adducts in high yields (up to 95%) and excellent enantioselectivities (up to 99%