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
Pyrrolidinyl-Camphor Derivatives as a New Class of Organocatalyst for Direct Asymmetric Michael Addition of Aldehydes and Ketones to β-Nitroalkenes
作者:Ying-Fang Ting、Chihliang Chang、Raju Jannapu Reddy、Dhananjay R. Magar、Kwunmin Chen
DOI:10.1002/chem.201000483
日期:——
Practical and convenient synthetic routes have been developed for the synthesis of a new class of pyrrolidinyl–camphor derivatives (7 a–h). These novel compounds were screened as catalysts for the direct Michael addition of symmetrical α,α‐disubstituted aldehydes to β‐nitroalkenes. When this asymmetric transformation was catalyzed by organocatalyst 7 f, the desired Michael adducts were obtained in