Ni-Catalyzed Highly Chemo-, Regio-, and Enantioselective Decarboxylative Aldol Reaction of β,γ-Unsaturated α-Ketoesters with β-Ketoacids

Molecular Iodine-Catalyzed N-Benzylic Sulfonamides C-N Bond Cleavage for the Decarboxylative Substitution of β-Keto Acids

Abstract:

A molecular iodine-catalyzed system for the decarboxylative substitution reactions of β-keto acids with N-benzylic sulfonamides via sp3 C-N bond cleavage has been disclosed. This procedure provides a series of α-functionalized ketones in good to excellent yields. Furthermore, the practicability of this method could be manifested efficiently in a gram-scale synthesis.

Water-mediated decarboxylative radical nitrosation of β-keto acids with tert-butyl nitrite: access to α-oximino ketones

A practical catalyst-free decarboxylative radical nitrosation system of β-keto acids with tert-butyl nitrite in water has been described.

β-Keto acids in asymmetric metal catalysis and organocatalysis

β-Keto acids, ideal surrogates of inactive ketones, play an important role in organic synthesis. The asymmetric decarboxylative reaction using β-keto acids is the one which is being studied the most. Herein we present a comprehensive review on this research topic, which is generally classified according to different catalytic systems and chiral induction modes. Additionally, some extended utilities of these methodologies for synthesizing bioactive compounds were also summarized. This review will facilitate the synthetic community to understand the role of β-keto acids in asymmetric reactions, providing many new opportunities for further exploration in this field.

Switching of Enantioselectivity in the Cu-Catalyzed Asymmetric Decarboxylative Aldol Reaction of Tryptanthrin with β-Keto Acids: An Unexpected Counteranion Effect

Cu-bisoxazoline-catalyzed enantioselective decarboxylative aldol reaction of tryptanthrin with aryl-substituted β-keto acids is developed, providing a straightforward approach to deliver a series of phaitanthrin A analogues. Both enantiomers of the products can be obtained with good to high enantioselectivity in the presence of a single chiral ligand by simply changing the copper salts. Based on the X-ray crystallographic analysis of chiral Cu(II)-bisoxazoline complexes, the tentative stereochemical models are presented to account for the observed counteranion-induced switching in enantioselectivity.

Pyridylacetic acids and related systems as alkylheteroarene surrogates in asymmetric decarboxylative Michael addition

In this manuscript, a novel method for the preparation of enantiomerically enriched pyridine derivatives has been described. It is based on the utilization of readily available 2-pyridylacetic acids as valuable synthons for the introduction of a pyridine ring in an asymmetric fashion. They have been used as pronucleophiles in asymmetric decarboxylative Michael addition to α,β-unsaturated aldehydes. The synthesis based on iminium activation using a chiral aminocatalyst that controlled the stereochemical outcome of the transformation has been successfully accomplished.

Stereoselective Copper-Catalyzed Direct Aldol Reaction of β, γ-Unsaturated α-Ketoesters with Coumaran-3-Ones

An efficient direct aldol reaction between coumaran-3-ones and β, γ-unsaturated α-ketoesters by virtue of a chiral copper complex is developed. A series of coumaran-3-one derivatives containing chiral tertiary alcohol structures are obtained in excellent yields and stereoselectivities.

The catalyst-free decarboxylative dearomatization of isoquinolines with β-keto acids and sulfonyl chlorides in water: access to dihydroisoquinoline derivatives

An efficient and concise catalyst-free one-pot synthetic protocol for obtaining dihydroisoquinoline derivatives has been developed via the three-component condensation of isoquinolines with β-keto acids and sulfonyl chlorides. This transformation involving decarboxylative dearomatization worked well under mild and water-mediated conditions. The protocol tolerates diverse functional groups, furnishing the dihydroisoquinoline products in good to excellent yields.

Organocatalytic asymmetric synthesis of β,β-diaryl ketones via one-pot tandem dehydration/1,6-addition/decarboxylation transformation of β-keto acids and 4-hydroxybenzyl alcohols

Herein we describe an organocatalytic protocol for the asymmetric synthesis of β,β-diaryl ketones. Under the catalysis of a chiral phosphoric acid, 4-hydroxybenzyl alcohols underwent dehydration to form para-quinone methides, which reacted with β-keto acids in 1,6-addition reactions. Upon treatment with Et₃N in one-pot, decarboxylation proceeded to provide the desired chiral ketones in nearly quantitative yields with high enantioselectivities.

Ni(II)-Catalyzed Enantioselective Synthesis of β-Hydroxy Esters with Carboxylate Assistance

A Ni-oxazoline complex-catalyzed asymmetric decarboxylative aldol reaction between malonic acid half-oxyesters and various carbonyls with carboxylate assistance was developed, affording structurally diverse β-hydroxy esters with good yields and enantioselectivities under mild conditions. Importantly, the broad substrate scope of this methodology enabled rapid accesses to several natural products and their analogues as exemplified by phenylpropanoid, phaitanthrin B, and phthalide.

Enantioselective Synthesis of Chromanones Bearing an α,α-Disubstituted α-Amino Acid Moiety via Decarboxylative Michael Reaction

In this manuscript, a novel, decarboxylative Michael reaction between α-substituted azlactones and chromone-3-carboxylic acids is described. The reaction proceeds in a sequence Michael addition followed by decarboxylative deprotonation, and it results in the formation of chromanones bearing an azlactone structural unit. The possibility of transforming an azlactone moiety into a protected α,α-disubstituted α-amino acid derivative is also demonstrated.

Nickel/Copper Dual Catalysis for Sequential Nazarov Cyclization/Decarboxylative Aldol Reaction

A nickel/copper cocatalyzed sequential Nazarov cyclization/decarboxylative aldol reaction is reported. Various β-hydroxycyclopentenones containing three contiguous stereocenters were prepared in good yields with high diastereoselectivities. A gram-scale reaction and further derivatizations were easily achieved to highlight the synthetic utility of this transformation. Preliminary attempts for sequential asymmetric transformation were also conducted.

Organocatalytic Asymmetric Decarboxylative Mannich Reaction of β-Keto Acids with Cyclic α-Ketiminophosphonates: Access to Quaternary α-Aminophosphonates

An organocatalytic asymmetric decarboxylative Mannich reaction of β-keto acids with cyclic α-ketiminophosphonates has been developed. By using saccharide-derived bifunctional amine-thiourea catalysts bearing an axial chiral binaphthyl scaffold, a wide range of quaternary α-amino-γ-oxophosphonates were obtained in up to 93% yield and >99% ee. Furthermore, two interesting α-aminophosphonate derivatives were synthesized from the corresponding decarboxylative Mannich product via simple transformations.

Catalytic enantioselective aldol reactions

Recent developments in catalytic asymmetric aldol reactions have been summarized.

Organocatalyzed Asymmetric Michael Addition of 1-Acetylindolin-3-ones to β,γ-Unsaturated α-Ketoesters: An Access to Chiral Indolin-3-ones with Two Adjacent Tertiary Stereogenic Centers

Asymmetric Michael addition of 1-acetylindolin-3-ones to β,γ-unsaturated α-ketoesters was investigated for the synthesis of chiral indolin-3-ones with two adjacent tertiary stereogenic centers. Under the catalysis of a chiral bifunctional squaramide derived from l-tert-leucine, a wide range of 1-acetylindolin-3-ones and β,γ-unsaturated α-ketoesters were well-tolerated in this transformation to provide the corresponding novel densely functionalized chiral indolin-3-one derivatives in high yield with excellent diastereo- and enantioselectivity under mild reaction conditions.

Didecarboxylative Iron-Catalyzed Bidirectional Aldolization towards Diversity-Oriented Ketodiol Synthesis

1,3-Acetonedicarboxylic acid was selectively activated by Fe(acac)3 , providing a synthetic platform for rapid synthesis of keto-3,3'-diols. The bidirectional aldol reaction was efficient for challenging aliphatic aldehydes, providing a rapid route to potentially bioactive complex structures.