In search of diamine analogs of the α,α-diphenyl prolinol privileged chiral organocatalyst. Synthesis of diamine derivatives of α,α-diphenyl-(S)-prolinol and their application as organocatalysts in the asymmetric Michael and Mannich reactions
摘要:
This paper describes improved reaction conditions for the substitution of the hydroxyl group in (S)-diphenyl(pyrrolidin-2-yl)methanol by the azide group, which was then reduced to the diamine derivative. We examined two protecting groups (N-Bn and N-Boc) on the pyrrolidine nitrogen in order to functionalize the primary amino group into various amide, alkylated amine, sulfonamide, thiourea and triazole derivatives. Notably, carefully controlled conditions were required to generate the desired derivatives from the sterically hindered benzhydrylamine moiety. Unexpectedly, upon removal of the N-protecting group in derivatives containing electrophilic polar double bonds (C=S, C=O) cyclization took place, affording products such as amidines. The target compounds were evaluated as bifunctional organocatalysts in the asymmetric Michael and Mannich addition reactions. (S)-2-(Azidodiphenylmethyl) pyrrolidine (S)-7 was identified as the most efficient organocatalyst among the various diamine derivatives of alpha,alpha-diphenyl-(S)-prolinol prepared in this work. (C) 2015 Elsevier Ltd. All rights reserved.
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.
Readily available chiral thioureas derived from cyclohexane-1,2-diamine were prepared and found to be highly effective organocatalysts for the conjugate addition of aldehydes and ketones to nitroalkenes. Excellent enantioselectivities and yields were obtained for a variety of aryl and heteroaryl nitroalkenes. The base additives are essential for good yields and excellent enantioselectivities in this
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
Pyrrolidine-Camphor Derivative as an Organocatalyst for Asymmetic Michael Additions of α,α-Disubstituted Aldehydes to β-Nitroalkenes: Construction of Quaternary Carbon-Bearing Aldehydes under Solvent-Free Conditions
Abstractmagnified imageA novel pyrrolidine‐camphor organocatalyst 3 was designed, synthesized and proven to be an efficient catalyst for the asymmetric Michael reaction. Treatment of α,α‐disubstituted aldehydes with β‐nitroalkenes in the presence of 20 mol% organocatalyst 3 and 20 mol% benzoic acid under solvent‐free conditions provided the desired Michael product possessing an all‐carbon quaternary center with high chemical yields (up to 99% yield) and high levels of enantioselectivities (up to 95% ee).
In search of diamine analogs of the α,α-diphenyl prolinol privileged chiral organocatalyst. Synthesis of diamine derivatives of α,α-diphenyl-(S)-prolinol and their application as organocatalysts in the asymmetric Michael and Mannich reactions
This paper describes improved reaction conditions for the substitution of the hydroxyl group in (S)-diphenyl(pyrrolidin-2-yl)methanol by the azide group, which was then reduced to the diamine derivative. We examined two protecting groups (N-Bn and N-Boc) on the pyrrolidine nitrogen in order to functionalize the primary amino group into various amide, alkylated amine, sulfonamide, thiourea and triazole derivatives. Notably, carefully controlled conditions were required to generate the desired derivatives from the sterically hindered benzhydrylamine moiety. Unexpectedly, upon removal of the N-protecting group in derivatives containing electrophilic polar double bonds (C=S, C=O) cyclization took place, affording products such as amidines. The target compounds were evaluated as bifunctional organocatalysts in the asymmetric Michael and Mannich addition reactions. (S)-2-(Azidodiphenylmethyl) pyrrolidine (S)-7 was identified as the most efficient organocatalyst among the various diamine derivatives of alpha,alpha-diphenyl-(S)-prolinol prepared in this work. (C) 2015 Elsevier Ltd. All rights reserved.