Diastereoselective Michael Reaction Research Articles

Chiral anthranilic pyrrolidine as custom-made amine catalyst for enantioselective Michael reaction of nitroalkenes with carbonyl compounds.

A chiral anthranilic pyrrolidine catalyst as a custom-made amine-catalyst was developed for the enantio- and diastereo selective Michael reaction of nitroalkenes with carbonyl compounds. In particular, a peptide-like catalyst in which an α-amino acid is attached to the anthranilic acid skeleton induced the high stereoselectivity of the reaction with aldehydes. Studies of the reaction mechanism indicated that the catalyst exhibits a divergent stereocontrol in the reaction, namely, steric control by a 2-substituted group on the catalyst and hydrogen-bonding control by a carboxylic acid group on the catalyst.

Asymmetric Synthesis of 3,4‐Dihydrocoumarins Bearing an α,α‐Disubstituted Amino Acid Moiety

AbstractAn organocatalytic approach for the stereoselective synthesis of 3,4‐dihydrocoumarins with an α,α‐disubstituted amino acid moiety incorporated is presented. The developed methodology is based on the cascade reaction between α‐substituted azlactones and 2‐hydroxychalcones. It is initiated by a chiral Brønsted base‐catalyzed enantio‐ and diastereoselective Michael reaction followed by the azlactone ring opening to construct a 3,4‐dihydrocoumarin framework. Products bearing two adjacent stereogenic centers, one being quaternary, were formed with high enantioselectivities and excellent diastereoselectivities. Furthermore, the complete regioselectivity of the new cascade reactivity is worthy of notice.magnified image

Concise Enantioselective Synthesis of Oxygenated Steroids via Sequential Copper(II)-Catalyzed Michael Addition/Intramolecular Aldol Cyclization Reactions.

A new scalable enantioselective approach to functionalized oxygenated steroids is described. This strategy is based on chiral bis(oxazoline) copper(II) complex-catalyzed enantioselective and diastereoselective Michael reactions of cyclic ketoesters and enones to install vicinal quaternary and tertiary stereocenters. In addition, the utility of copper(II) salts as highly active catalysts for the Michael reactions of traditionally unreactive β,β'-enones and substituted β,β'-ketoesters that results in unprecedented Michael adducts containing vicinal all-carbon quaternary centers is also demonstrated. The Michael adducts subsequently undergo base-promoted diastereoselective aldol cascade reactions resulting in the natural or unnatural steroid skeletons. The experimental and computational studies suggest that the torsional strain effects arising from the presence of the Δ(5)-unsaturation are key controlling elements for the formation of the natural cardenolide scaffold. The described method enables expedient generation of polycyclic molecules including modified steroidal scaffolds as well as challenging-to-synthesize Hajos-Parrish and Wieland-Miescher ketones.

Highly Diastereoselective Michael Reactions Using β-Nitrocarbonyl Nucleophiles.

We have discovered a highly diastereoselective Michael reaction of α-substituted, β-nitrocarbonyl compounds to deliver highly functionalized stereodiads containing fully substituted nitrogen-bearing centers. Good to excellent yields and diastereoselectivities are observed. This transformation is tolerant of various types of carbonyl groups on the nucleophilic partner, as well as a range of unsaturated electrophiles. Mechanistic investigations are consistent with internal hydrogen bonding in the nitroalkane tautomer as the major factor in the control of diastereoselectivity in these transformations.

Selective Michael Reaction Controlled by Supersilyl Protecting Group

AbstractSelective Michael reaction of organolithium reagents to supersilyl methacrylate is reported. The method was able to control a single and double Michael addition. The successful termination of the process using the supersilyl protecting group allows for the controlled, chemoselective, and diastereoselective Michael reaction.

Selective Michael Reaction Controlled by Supersilyl Protecting Group.

Selective Michael reaction of organolithium reagents to supersilyl methacrylate is reported. The method was able to control a single and double Michael addition. The successful termination of the process using the supersilyl protecting group allows for the controlled, chemoselective, and diastereoselective Michael reaction.

ChemInform Abstract: Chiral Amine Catalyzed Enantio‐ and Diastereoselective Michael Reaction in Brine.

Abstract Simple pyrrolidine-based chiral amines were synthesized and used for the Michael addition of different ketones to a variety of nitro-olefins in brine. The effect of different surfactants and acids on the yields and stereochemical outcome of the Michael adducts was studied in detail. Chiral amine 1g was found to catalyze the formation of Michael adducts with high enantioselectivity (up to >99%), diastereoselectivity [up to 98:2 ( syn : anti )] and yield (up to 94%).

Chiral amine catalyzed enantio- and diastereoselective Michael reaction in brine

Simple pyrrolidine-based chiral amines were synthesized and used for the Michael addition of different ketones to a variety of nitro-olefins in brine. The effect of different surfactants and acids on the yields and stereochemical outcome of the Michael adducts was studied in detail. Chiral amine 1g was found to catalyze the formation of Michael adducts with high enantioselectivity (up to >99%), diastereoselectivity [up to 98:2 (syn:anti)] and yield (up to 94%).

Diastereoselective Michael reaction of chiral nickel(II) glycinate with nitroalkenes for asymmetric synthesis of β-substituted α,γ-diaminobutyric acid derivatives in water

We have developed the first operationally simple and environmentally benign protocol for the aqueous asymmetric Michael addition reaction of chiral nickel(II) glycinate with nitroalkenes. The reactions proceeded smoothly in the presence of TBAB (tetrabutyl ammonium bromide) in neat water at room temperature and provided good yields of β-substituted α,γ-diaminobutyric acid derivatives with excellent diastereoselectivities.

Practical Synthesis of a Peptide Deformylase (PDF) Inhibitor

A practical chromatography-free synthesis of an N-formylated hydroxylamine peptide deformylase inhibitor LCD320 is described. A diastereoselective Michael reaction of (4S)-3-[2-(cyclobutylmethyl)-1-oxo-2-propenyl]-4-(phenylmethyl)-2-oxazolidinone with O-benzyl hydroxylamine was used to establish the key stereogenic center. We found that traces of residual Li+ from a previous step had a great impact on the diastereoselectivity of this reaction. A very efficient amidation coupling reaction of proline derivative (2S,4R)-4-fluoro-1,2-pyrrolidinedicarboxylic acid 1,1-dimethylethyl ester with weakly nucleophilic 3-pyridazinamine using methanesulfonyl chloride in the presence of 1-methylimidazole in DMF was also developed that proceeded without racemization.

Enantiodivergent synthesis of 3-amino-4,4-dimethyl-1-phenylpyrrolidin-2-one and derivatives: amino analogues of pantolactone

An enantiodivergent preparation of (+)-( R)- and (−)-( S)-3-amino-4,4-dimethyl-1-phenylpyrrolidin-2-one, ( R)- and ( S)- 9, and several derivatives, from 4,4-dimethyl-1-phenylpyrrolidin-2,3-dione, 4, and ( R)- or ( S)-1-phenylethylamine, ( R)- or ( S)- 5, as the chirality transfer agents, is described. Amine ( S)- 9 has also been used as a chiral auxiliary in a diastereoselective Michael reaction.

Enantio‐ and Diastereoselective Construction of Vicinal Quaternary and Tertiary Carbon Centers by Catalytic Michael Reaction of α‐Substituted β‐Keto Esters to Cyclic Enones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantio- and diastereoselective construction of vicinal quaternary and tertiary carbon centers by catalytic Michael reaction of α-substituted β-keto esters to cyclic enones

A catalytic enantio- and diastereoselective Michael reaction was achieved to construct vicinal quaternary and tertiary carbon centers in one step. Using 5 mol % of La(O- i-Pr) 3 and 10 mol % of a new N-linked-BINOL type ligand, the reaction of α-substituted β-keto esters to cyclic enones provided the corresponding Michael adducts in up to quantitative yield with a diastereomeric ratio up to 86/14 and enantiomeric excess up to 86% for the major isomer. An alternative catalyst preparation method using La(OTf) 3 instead of La(O- i-Pr) 3 was also examined.

Enantio‐ and Diastereoselective Michael Reaction of 1,3‐Dicarbonyl Compounds to Nitroolefins Catalyzed by a Bifunctional Thiourea.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantio‐ and Diastereoselective Michael Reaction of 1,3‐Dicarbonyl Compounds to Nitroolefins Catalyzed by a Bifunctional Thiourea.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Enantio- and Diastereoselective Michael Reaction of 1,3-Dicarbonyl Compounds to Nitroolefins Catalyzed by a Bifunctional Thiourea

We synthesized a new class of bifunctional catalysts bearing a thiourea moiety and an amino group on a chiral scaffold. Among them, thiourea 1e bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to nitroolefins. Furthermore, we have developed a new synthetic route for (R)-(-)-baclofen and a chiral quaternary carbon center with high enantioselectivity by Michael reaction. In these reactions, we assumed that a thiourea moiety and an amino group of the catalyst activates a nitroolefin and a 1,3-dicarbonyl compound, respectively, to afford the Michael adduct with high enantio- and diastereoselectivity.

Highly Diastereoselective Michael Reaction of (S)‐Mandelic Acid Enolate. Chiral Benzoyl Carbanion Equivalent Through an Oxidative Decarboxylation of α‐Hydroxyacids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The First Total Synthesis of (.+‐.)‐Ingenol.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Highly diastereoselective Michael reaction of (S)-mandelic acid enolate. Chiral benzoyl carbanion equivalent through an oxidative decarboxylation of α-hydroxyacids

The reaction of the lithium enolate of the 1,3-dioxolan-4-one derived from optically active (S)-mandelic acid and pivalaldehyde with α,β-unsaturated carbonyl compounds proceeds readily to give the corresponding Michael adducts in good yields and high diastereoselectivity. Subsequent basic hydrolysis of the acetal and oxidative decarboxylation of the α-hydroxyacid moiety provides chiral 2-substituted 1,4-dicarbonyl compounds with very high enantiomeric excesses.

The first total synthesis of (+/-)-ingenol.

The first total synthesis of (+/-)-ingenol has been achieved. The key features of the synthesis include the use of a highly diastereoselective Michael reaction to fix the C-11 methyl stereochemistry and the incorporation of the dimethylcyclopropane via diastereoselective carbene addition to the Delta13,14 olefin. The intramolecular dioxenone photoaddition-fragmentation sequence leads to the establishment of the critical C-8/C-10 trans intrabridgehead stereochemistry, a central challenge in the synthesis of ingenanes. The completion of the synthesis proceeds using the C-6alpha hydroxymethyl group as the sole handle for oxidation of seven contiguous carbon centers.