Acid Esters In Good Yields Research Articles

Concise Synthesis of Isocoumarin-3-carboxylic Acid Esters

A concise synthesis of isocoumarin-3-carboxylic acid ester derivatives has been developed by the Pd catalyzed one-pot fluorocarbonylation/lactonization/β-elimination cascade reaction starting from easily prepared hydroxyesters. ortho-Bromobenzaldehyde derivatives were converted to 2-chloro-1-hydroxy-2-arylpropionic acid esters in two steps via Darzens reaction. The resulting 1-hydroxypropionates were smoothly converted to isocoumarin-3-carboxylic acid esters in good yields by the newly developed cascade reaction in an efficient manner. The synthetic utility was demonstrated by the first total synthesis of penicipyran C. A new cascade reaction for synthesizing isocoumarin-3-carboxylic acid esters involving Pd-catalyzed fluorocarbonylation/lactonization/β-elimination was developed. The substrates for this cascade reaction were easily prepared from several ortho-bromobenzaldehydes. This cascade reaction gave several isocoumarin-3-carboxylic acid esters in good to excellent yield, and one of the resultant isocoumarin derivatives led to the first total synthesis of penicipyran C.

A Synthetic Approach to PW2‐Like Compounds

AbstractThe 9H‐xanthene derivatives, like PW2, displayed a wide spectrum of bioactivities. Herein, we reported a rapid and simple synthetic route for compounds containing the xanthenic moiety in their structure and amides. The efficient preparation of novel 1,8‐dioxo‐2,3,4,5,6,7,8,9‐octahydro‐1‐xanthen‐9‐yl‐ acetic acid alkyl esters by multicomponent tandem Michael‐cyclization reactions starting from cyclohexanediones and alkynes is described. Iodine and cerium (IV) ammonium nitrate were used for the oxidative aromatization step proving a series of 1,8‐mono and dialkoxy‐alkyl‐xanthenyl‐9‐yl acetic acid esters in good yields. The proposed mechanism for the oxidative aromatization involves several organic transformations. The final step was the incorporation of an amide to mimic the PW2 structure that was prepared by hydrolysis of the esters, followed by the amide formation using N,N‐dimethyl‐1,3‐ propandiamine, and benzylamine.

Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to Glyoxylates: Access to Optically Active Substituted Mandelic Acid Esters

A rhodium-catalyzed enantioselective addition of glyoxylates to arylboronic acids promoted by a simple chiral sulfinamide-based olefin ligand under mild reaction conditions is described. The reaction provides access to a variety of optically active substituted mandelic acid esters in good yields with up to 83% ee. The catalytic system is also applicable to pyruvate addition. The synthetic utility of this method is highlighted by a formal synthesis of the antiplatelet drug clopidogrel.

Inside Cover: Biomimetic Chiral Pyridoxal and Pyridoxamine Catalysts (Chin. J. Chem. 2/2019)

The inside cover picture shows the development of chiral pyridoxal and pyridoxamine catalysts by mimicking vitamin B6‐dependent enzymes. These chiral pyridoxals and pyridoxamines displayed extraordinary catalytic performances in asymmetric biomimetic transamination and Mannich reaction, to give various chiral α‐amino acids and α,β‐diamino acid esters in good yields with excellent diastero‐ and/or enantioselectivities. The research has provided some useful information for further applications of the catalytic power of vitamin B6 in the area of asymmetric cayalysis. More details are discussed in the article by Zhao et al. on page 103–112. image

ChemInform Abstract: Regioselective Alkylative Carboxylation of Allenamides with Carbon Dioxide and Dialkylzinc Reagents Catalyzed by an N‐Heterocyclic Carbene—Copper Complex.

AbstractThe reaction of allenamides with dialkylzinc reagents and CO2 proceeds smoothly in the presence of a catalytic quantity of [(IPr)CuCl] to afford (Z)‐α,β‐dehydro‐β‐amino acid esters in good yields.

A Disulfonimide Catalyst for Highly Enantioselective Mukaiyama–Mannich Reaction

A new BINOL-derived chiral disulfonimide has been developed by introducing 4-methyl-3,5-dinitrophenyl substituents at its 3- and 3'-positions. This chiral disulfonimide catalyst displays high catalytic efficacy toward the asymmetric Mukaiyama-Mannich reaction of imines with ketene silyl acetals leading to β-amino acid esters in good yields (up to 99%) with high diastereoselectivities (syn/anti up to 97:3) and enantioselectivities (up to 98% ee). The long-standing problem of the chiral phosphoric acid-catalyzed asymmetric Mukaiyama-Mannich reaction that requires a 2-hydroxyphenyl moiety was solved by this disulfonimide catalyst.

Regioselective Alkylative Carboxylation of Allenamides with Carbon Dioxide and Dialkylzinc Reagents Catalyzed by an N-Heterocyclic Carbene-Copper Complex.

The alkylative carboxylation of allenamide catalyzed by an N-heterocyclic carbene (NHC)-copper(I) complex [(IPr)CuCl] with CO2 and dialkylzinc reagents was investigated. The reaction of allenamides with dialkylzinc reagents (1.5 equiv) and CO2 (1 atm.) proceeded smoothly in the presence of a catalytic quantity of [(IPr)CuCl] to afford (Z)-α,β-dehydro-β-amino acid esters in good yields. The reaction is regioselective, with the alkyl group introduced onto the less hindered γ-carbon, and the carboxyl group introduced onto the β-carbon atom of the allenamides. The first step of the reaction was alkylative zincation of the allenamides to give an alkenylzinc intermediate followed by nucleophilic addition to CO2 . A variety of cyclic and acyclic allenamides were found to be applicable to this transformation. Dialkylzinc reagents bearing β-hydrogen atoms, such as Et2 Zn or Bu2 Zn, also gave the corresponding alkylative carboxylation products without β-hydride elimination. The present methodology provides an easy route to alkyl-substituted α,β-dehydro-β-amino acid ester derivatives under mild reaction conditions with high regio- and stereoselectivtiy.

Highly Enantioselective Michael Addition of Malonates to β‐CF3‐β‐(3‐Indolyl)nitroalkenes: Construction of Trifluoromethylated All‐Carbon Quaternary Stereogenic Centres

AbstractA family of γ‐nitrobutyric acid esters bearing an all‐carbon quaternary stereogenic centre have been synthesized. Chiral thioureas catalysed the conjugate addition of malonates to nitroalkenes containing a trifluoromethyl and indole motif at the β‐position to afford the corresponding γ‐nitrobutyric acid esters in good yields (up to 89 % yield) and with good to excellent enantioselectivities (up to 90 % ee). This protocol provides an efficient access to optically enriched γ‐amino acids and β‐disubstituted γ‐butyrolactams.

ChemInform Abstract: Palladium‐Catalyzed β‐Arylation of Silyl Ketene Acetals and Application to the Synthesis of Benzo‐Fused δ‐Lactones.

AbstractSilyl ketene acetals show enhanced chemoselectivity as nucleophiles in Pd‐catalyzed migrative C(sp3)‐H arylations with aryl bromides to give arylpropionic acid esters in good yields.

Selective synthesis of thiodiglycol dicarboxylic acid esters via p-TsOH/C-catalysed direct esterification

The esterification of thiodiglycol and long alkyl-chain carboxylic acids is reported. Reaction of thiodiglycol with carboxylic acid via p-TsOH/C-catalysed direct esterification afforded thiodiglycol dicarboxylic acid esters in good yields and chemoselectivity. The use of immobilized p-TsOH on activated carbon as catalyst is crucial for the transformation. The immobilized p-TsOH on activated carbon is used as catalyst for the transformation of thiodiglycol with long alkyl-chain carboxylic acids to the corresponding thiodiglycol dicarboxylic acid esters. The direct esterification is carried out in xylene to remove the water generated in the reaction azeotropically and affords good yields and chemoselectivity.

Diastereoselective three-component reactions of aryldiazoacetates with alcohols/water and alkynals: application to substituted enelactones

Dirhodium acetate catalyzed three-component reactions of aryl diazoacetates, alcohols or water, and 2-alkynals are reported to afford β-alkynyl α,β-dihydroxyl acid esters in good yield with high diastereoselectivity. Synthetic utility of the reaction was demonstrated in the conversion of the versatile alkynyl functionality to other synthetically useful compounds, including efficient synthesis of 2-aryl-2,3-dihydroxyl enelactones.

Catalytic Asymmetric Mannich Reaction of Glycine Derivatives with N‐Tosylimines using Copper(I)/TF‐BiphamPhos Complex

AbstractThe direct asymmetric Mannich reaction of glycine Schiff bases with N‐tosylimines has been developed with the tetrakis(acetonitrile)copper(I) tetrafluoroborate [Cu(CH3CN)4BF4]/TF‐BiphamPhos complex. This catalytic system performs well over a broad range of substrates, furnishing anti‐adducts of various α,β‐diamino acid esters in good yields with up to 94:6 diastereoselectivity and 97% enantioselectivity.

Synthesis of uracil derivatives and their alkylation: an approach to peptide non-nucleic acid monomers

N3-substituted 5-acetyluracils derived from corresponding N3-substituted 5-acetylcytosines are versatile functional precursors that allow the introduction of various aliphatic, aromatic, carbocyclic, and carbamoyl functionalities at N1-position. A series of 1,3-disubstituted 5-acetyluracils were synthesized by alkylation at N1-position. For the introduction of carbamoyl functionalities a convergent approach is studied, leading to N-arylacetamide derivatives; the linear approach furnished peptide non-nucleic acid monomers by replacement of active ester with amino acid esters in good yields.

Preparation of Pentafluorosulfanyl (SF5) Pyrrole Carboxylic Acid Esters

Pyrrole derivatives bearing a pentafluorosulfanyl group are currently unknown. In this paper, a facile preparation of SF5-substituted pyrrole carboxylic acid esters in good yield is reported. Utilizing the cycloaddition of an azomethine ylide to pentafluorosulfanylalkynes, a series of dihydropyrroles were prepared and oxidized to the respective 1-tert-butyl-4-(pentafluorosulfanyl)pyrrole-2-carboxylic acid esters in good yield. Further treatment of these pyrroles with catalytic triflic acid allowed removal of the tert-butyl group.

Synthesis of Novel Silylated 1,2,4‐Triazin‐5‐ones.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Synthesis of β‐Amino Acids by Use of Ketene Diethyl Acetal as Enolate Equivalent.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis of novel silylated 1,2,4-triazin-5-ones

The reaction of various α-silyl-α-keto esters with thiosemicarbazide at 50 °C in ethyl acetate was found to give α-silyl-substituted thiosemicarbazone-acetic acid esters in good yield. These may then be converted to their corresponding silyl-substituted 1,2,4-triazin-5-ones by cyclization under basic conditions.

A new synthesis of β-amino acids by use of ketene diethyl acetal as enolate equivalent

Reaction of phenylsulfonyl formamides, readily available in a single step from an aromatic aldehyde and sodium phenylsulfinate, with ketene diethyl acetal under basic conditions gives N-formyl β-amino acid esters in good yield, which can be kinetically resolved with a lipase.

Environmentally Benign Process for the Synthesis of N‐Formyl Amino Acid Esters.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Environmentally benign process for the synthesis of N-formyl amino acid esters

Several amino acid ester hydrochlorides were reacted with ammonium formate to give N-formyl amino acid esters in good yields.