Solvolysis of 1-Chloro-1-Alkenyl Phenyl Sulfides. Synthesis of α-Bromo Phenyl Thiocarboxylic Esters, α-Bromo Alkyl Carboxylic Esters and α-Phenylthio Methyl Carboxylic Esters

1-chloro-1-alkenyl phenyl sulfides treated with bromine followed by hydrolysis or methanolysis give α-bromo phenyl thiocarboxylic esters and α-phenyl-thio methyl carboxylic esters. Direct oxidative solvolysis with bromine and alcohol give α-bromo alkyl carboxylic esters.     

Intelligence Way from Eco-friendly Synthesis Strategy of New Heterocyclic Pyrazolic Carboxylic α-Amino Esters

The α-amino acid derivatives constitute a class of compounds of particular medicinal and synthetic attention and considerable interest has been devoted to their synthesis in recent years. In the present work, we develop the computational study of the synthesis reaction of new pyrazolyl α-amino esters derivatives using the Gaussian 09 based on the DFT/B3LYP density functional theory method, with the base 6-31G(d, p) to ensure the possibility of carrying out these reactions within the laboratory of synthesis. Indeed, this research has encouraged us to establish an economical synthesis strategy of these products in overall yields of 73.5% to 87% to have access to new active biomolecule through the O-alkylation reaction between methyl α-azidoglycinate N-benzoylated and primary pyrazole alcohols[(3,5-dimethyl-1H-pyrazol-1-yl)methanol, (1H-pyrazol-1-yl)methanol and (3-ethoxy-5-methyl-1H-pyrazol-1-yl)methanol] under different operating conditions. The structure of the prepared heterocyclic systems was characterized by conventional spectroscopic techniques, like ¹H NMR, ¹³C NMR, and MS. The results revealed that the experimental study is in good correlation with the computational one.     

Synthesis of α-Arylated Esters from Aryl Halides

The preparation of α-arylalkanoic acid esters has received significant attention, not only due to these compounds are important industrial materials, but also some of them are nonsteroidal anti-inflammatory drugs (NSAID)1. Arylation of β-dicarbonyl carb…     

The Structure and Spectroscopy of α-Hydroxyphosphonates

Abstract

α-Hydroxyphosphonates are important intermediates in the preparation of various organophosphorus compounds. Methods for their preparation have been described.¹ We now report new aspects of their structure and spectroscopy. In the solid state, O,O-dimethyl α-hydroxy-α-phenyl-β-chloroethylphosphonate has been shown by X-ray diffraction studies to consist of hydrogen-bonded dimers with a hydrosen-bond length between the phosphoryl oxygen and hydroxyl hydrogen atom of 1.74 Å. The P=0 bond is relatively short (1.463).     

Diastereoselective α-Alkylation of β-Amino Esters: Preparation of Novel α-Substituted β-Amino Esters from α-Amino Acids

b-Amino acids and their derivatives have attracted considerable attention in recent years due to their occurrence in biologically active natural products, such as dolastatins 11, cyclohexylnorstatine 22 and taxol 33. bAmino acids also find application in the synthesis of blactams4, piperidines5, indolizidines6. Moreover, the peptides consisting of bamino acids, the so called bpeptides, have been extensively studied recently7. Consequently, considerable efforts have been directed to the synt…     

Influence of Carboxylic Acids on the Synthesis of Chlorohydrin Esters from 1,3‐Butanediol

The influence of diverse carboxylic acid on the preparation of chlorohydrin esters using a one‐pot esterification–chlorination reaction, in which one of the reagents (chlorotrimethylsilane) acts as solvent, is described. Whereas the acid with low pKa provided higher amounts of the 2‐chloro regioisomer, the ones with higher pKa rendered the 1‐chloro regioisomer in 80% yield. These results are in accordance with the mechanism proposed in a previous article.     

Reactions of α-Hydroxyphosphonates under PTC Conditions

Abstract

We found, that dialkyl phosphite 1 and oxo-compound 2 in an equilibrium reaction give an adduct α-hydroxyphosphonate 5 un -der phase-transfer catalytic conditions [K₂CO₃/TEBA/dichloroethane or aromatic solvents (solid-liquid PTC); 50% NaOH/TEBA/dichloroethane or benzene (liquid-liquid PTC)]. On the other hand 3, is transformed to phosphate 4 or to α-alkoxyphosphonate 5 in the presence of alkylating agent using PTC circumstances.     

Influence of the Solvation Upon the Reaction of α-Cyclodextrin with Carboxylic Acids,Their Methyl Esters,and Their Sodium Salts in Aqueous Solution Studied by Calorimetric Measurements

The complex formation of α-cyclodextrin with carboxylic acids, their methyl esters, and their sodium salts has been studied using calorimetric titrations. The stronger solvation of the carboxylic sodium salts compared with the free acid or their methyl esters lowers the values of the reaction enthalpy and entropy. Complex formation is influenced in the positive direction by the release of “high-energy water” from the cavity of α-cyclodextrin. The values of the reaction enthalpy and entropy increase for the complex formation of α-cyclodextrin with increasing chain length of the carboxylic acids and their derivatives, and reach an approximately constant upper limit in the case of five methylene groups.     

Boron-Catalyzed α-Functionalizations of Carboxylic Acids

Catalytic, chemoselective, and asymmetric α-functionalizations of carboxylic acids promise up-grading simple feedstock materials to value-added functional molecules, as well as late-stage structural diversifications of multifunctional molecules, such as drugs and their leads. In this personal account, we describe boron-catalyzed α-functionalizations of carboxylic acids developed in our group (five reaction types). The reversible boron carboxylate formation is key to the acidification of the α-protons and enolization using mild organic bases, allowing for chemoselective and asymmetric bond formations of carboxylic acids. The ligand effects on reactivity and stereoselectivity, substrate scopes, and mechanistic insights are summarized.     

Aqueous-Phase Synthesis of α-Hydroxyphosphonates Catalyzed by β-Cyclodextrin

α-Hydroxyphosphonates were synthesized from aromatic/heteroaromatic aldehydes with triethyl phosphite in the presence of β-cyclodextrin in an aqueous medium. The β-cyclodextrin can be recovered and reused without loss of catalytic activity.     

A Substrate-Driven Approach to Determine Reactivities of α,β-Unsaturated Carboxylic Esters Towards Asymmetric Bioreduction

The degree of C?C bond activation in the asymmetric bioreduction of α,β-unsaturated carboxylic esters by ene-reductases was studied, and general recommendations to render these "borderline-substrates" more reactive towards enzymatic reduction are proposed. The concept of "supported substrate activation" was developed. In general, an additional α-halogenated substituent proved to be beneficial for enzymatic activity, whereas β-alkyl or β-aryl substituents were detrimental for the reactivity of nonhalogenated substrates, and α-cyano groups showed little effect. The alcohol moiety of the ester functionality was found to have a strong influence on the reaction rate. Overall, activities were determined by both steric and electronic effects.     

New Cyclolignan Esters and Their Antidiabetic Activitity from the Root of Rhus semialata

Rhus semialata is one of five Rhus species (Anacardiaceae), distributed in the island of Taiwan. In the early days,the pericarp of R. semialata was commonly used as a substitute of salt by indigenous mountain people. The root of it is also a folk herb for treating diarrhea, spermatorrhea and malaria.[1,2] This paper describes the isolation and structural elucidation of new cyclolignan esters 3 and 4, and two known compounds: cyclolariciresinol (1) and lynoiresinol (2) isolated from the n-butanol extract of R. semialata.     

Base Promoted Rearrangement of Carbonate Esters Derived from Aldehyde Cyanohydrins: Application to the Synthesis of α-Keto Esters

Acylation of the cyanohydrin derivative (2) of representative aldehydes with ethyl chloroformate, followed by treatment of the corresponding mixed carbonate esters (3) with lithium hexamethyldisilazide, afforded the cyanohydrin derivative (4) of α-keto esters. Cleavage of the latter (4) with 2,6-lutidine in the presence of silver nitrate led to the procurement of α-keto esters in >50% overall yield.     

A Convenient Synthesis of Vinyl Epoxides from Glycidic Esters via α-Hydroxy-β,γ-unsaturated Esters

Glycidic esters, upon isomerisation with BF₃.Et₂O yield α-hydroxy-β,γ-unsaturated esters. These are then reduced with LiAlH₄ to vicinal diols which are converted to vinyl epoxides in two steps.     

Stereoselective Aldol Reaction of α-Phenylseleno Esters

Abstract

The TiCl₄-catalyzed reaction of a-phenylseleno esters with aldehydes in the presence of Ph₃P or Ph₃P=O gives aldol products with high syn selectivity.     

Polymer Supported Synthesis of 2,3,4,6-Tetra-O-Acetyl-β-D-Glucopyranosyl Esters of Aromatic Carboxylic Acids

Aromatic carboxylic acids bound to Amberlyst A-26 react with α-acetobromoglucose to form 2,3,4,6-tetra-O-acetyl-1-0-aroyl-β-D-glucopy ranose derivatives in good yield. Glucosylation occurs satisfactorily with carboxylic acids and nitrophenols (pKa 7–4), but not with phenols whose pKa values are higher (pka ～ 10). Selective glucosylation at the carboxylic group is easily achieved in the case of phenolic acids.     

Convenient Synthesis of Vinyldiazomethanes from α-Diazo-β-Keto Esters and Related Systems

A series of vinydiazomethanes were readily prepared by sodium borohydride reduction of a-diazo-p-ketoesters followed by phosphorus oxychloride induced dehydration of the resulting a-diazo-p-hydroxyesters.     

Synthesis of Phosphonic Acids Related to the Antibiotic Fosmidomycin from Allylic α- and γ-Hydroxyphosphonates

Abstract

Fosmidomycin is the most active compound of a group of natural phosphonic acid antibiotics bearing a unique hydroxamic acid functionality in the γ-position¹. We present here two efficient and novel routes to precursors and analogues of these compounds.     

A New Synthesis of α-Aryltelluro Esters

Aryltellurenyl iodides react with Reformatsky reagents in dry THF at room temperature rapidly to produce α-aryltelluro esters in good yields.     

[Bmim]OAc Catalyzed Michael Addition of Active Methylene to α,β-Unsaturated Carboxylic Esters and Nitriles

<正>Michael addition of active methylene compounds toα,β-unsaturated carboxylic esters and nitriles was effectively catalyzed by a basic ionic liquid,1-butyl-3-methylimidazolium acetate([Bmim]OAc).The bis-addition products were selectively obtained in high yields under miLd reaction conditions.