SOLID STATE SYNTHESIS OF SUBSTITUTED COUMARIN-3-CARBOXYLIC ACIDS VIA THE KNOEVENAGEL CONDENSATION UNDER MICROWAVE IRRADIATION

Synthesis of substituted coumarin-3-carboxylic acids using the Knovenagel reaction of malonic acid and O-hydroxyaryl aldehydes supported onto HZSM-5 zeolite under microwave irradiation is described.     

Synthese von 1,6-Trimethylen-3-methoxycarbonyl-4-methyl-2-pyridon

The reaction sequences shown in schemes 3 and 4, represent a new method for the synthesis of a substituted pyridone-system, starting from a vinylogous amide or thioamide and malonic ester.     

One-pot two-step synthesis of 4-vinylphenols from 4-hydroxy substituted benzaldehydes under microwave irradiation: a new perspective on the classical Knoevenagel-Doebner reaction

The classical Knoevenagel-Doebner reaction is reinvestigated wherein the direct synthesis of substituted 4-vinylphenols instead of the expected 4-hydroxycinnamic acids is described. The condensation reaction is performed on 4-hydroxy substituted benzaldehydes and malonic acid with a mixture of acetic acid-piperidine as condensing agent under focused microwave irradiation. The occurrence of simultaneous condensation-double decarboxylation without the use of any decarboxylating agent is a new finding, the reaction being facilitated solely by the hydroxy substituent and microwave irradiation effect.     

A novel transformation in the quadrone series

A remakable reaction of the substituted bicyclo [3,3,0] oct-3-ene-2-one ($\text{2e}$) with the sodium enolate of malonic ester is described.     

Malonic to Acetic Ester Transformation by Boric Acid

One of our synthetic projects involves a step of removing a carbalkoxy group from a substituted malonic ester. For accomplishing that goal, Krapcho's method¹ was deemed unsuitable, because the malonic ester contains an allylic halogen which is liable to attack by dimethyl sulfoxide (Kornblum reaction). Our recent work on using iodotrimethylsilane² to achieve decarbal-koxylation of such esters was partly impelled by that need; however, the prohibitive economics associated with even a medium-scale preparation forced us to develop a less expensive alternative.     

The α-arylation of derivatives of malonic acid with aryllead triacetates. New syntheses of ibuprofen and phenobarbital.

Derivatives of Meldrum's acid and the sodium salts of substituted malonic esters undergo rapid arylation in high yield when treated with aryllead triacetates. These reactions have been applied to the synthesis of ibuprofen, an analgesic, and in a closely related reaction 5-ethylbarbituric acid has been reacted with phenyllead triacetate to give phenobarbital.     

Michael addition approach for the synthesis of novel spiro compounds and 2-substituted malonic acid derivatives from Meldrum’s acid

Novel routes for the synthesis of spiro derivatives of Meldrum’s acid and 2-substituted malonic acid derivatives have been developed. Meldrum’s acid was monoalkylated using a Michael addition reaction. Mono-Michael adducts were then alkylated using substituted haloalkanes, which on condensation gave spiro derivatives of Meldrum’s acid. Bis Michael addition of Meldrum’s acid with 1,5-diaryl-1,4-pentadien-3-one gave directly a spiro derivative of Meldrum’s acid. These compounds and bis alkylated Meldrum’s acid derivatives, on acidic methanolysis gave 2-substituted malonic acids.     

Three-component, one-pot sequential synthesis of N-aryl, N'-alkyl barbiturates

[reaction: see text] Condensation between N-alkyl, N'-aryl carbodiimides and malonic acid monoesters leads to a high-yield formation of N-acyl urea derivatives that could be cyclized to C-monosubstituted barbiturates by addition of a suitable base in a one-pot sequential fashion. In the presence of an electrophile, the last step gives rise to a one-pot, three-component sequential synthesis of fully substituted barbiturates.     

Preparation of substituted cinnamic acids labelled with deuterium and tritium at the ring positions

A series of substituted cinnamic acids labelled at the ring positions with deuterium or tritium has been easily obtained via the Doebner modification of Knoevenagel condensation reaction between labelled benzaldehyde derivatives and malonic acid in pyridine. The substituted benzaldehyde precursors were synthesized by isotope exchange method in deuterated or tritiated water at 80 °C in acidic medium. Ring-tritiated substituted cinnamic acids with specific activity ranging from 207 GBq /5.6 Ci/ mol^–1 to 4366 GBq /118 Ci/ mol^–1 was obtained using ca. 37 GBq /1 Ci/ of HTO.     

Synthese de dienes gem-diactives : Selon une condensation apparentee a la reaction de stobbe

Condensation of carbonyl compounds with alkylidene cyanacetic esters using an equivalent of base, affords a new route to gem-diactivated dienes or trienes. The synthetic utility of the reaction is discussed with respect to the structure of the reactants. Configurations are determined by NMR after photoisomerisation experiments. Isolation of some δ-lactones, intermediates of the reaction, allows an interpretation of the mechanism and stereospecificity.     

Synthesis of new pyrrolidone derivatives

Reaction of N-chloromethylpyrrolidone with the sodio-derivatives of malonic and substituted malonic esters in dry ether has given the diethyl esters of the corresponding 2-oxopyrrolidinomethylmalonic acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1201–1202, September, 1970.     

One-pot preparation of phenylpropanoid esters co-catalyzed by boric acid and piperidine

Phenylpropanoid esters, especially those with hydroxyl and/or methoxy groups on the benzene ring, are important medicinal chemicals or intermediates. They are usually prepared by esterification of their corresponding substituted cinnamic acids with various alcohols. However, the esterification procedures often suffer from environmentally hazardous problems when sulfuric acid is used as a catalyst or suffer from unsatisfactory yields and expensive raw material when enzyme is applied as a catalyst. In this paper, a convenient one-pot process for preparing various phenylpropanoid esters from substituted benzaldehydes bearing hydroxyl and/or methoxyl groups has been developed. The alcohols react first with malonic acid catalyzed by boric acid to form monomalonate, then without separation, let the resultant mixture immediately react with the injected various substituted benzaldehydes in the presence of piperidine to afford the desired esters with moderate to good yields.     

Decarboxylative Mannich Reactions with N-Alkyl Imines

The use of N-alkyl imines in decarboxylative Mannich reaction with substituted malonic acids half oxyesters (SMAHOs) has been developed to afford a direct access to secondary β^2,3-aminoesters. The transformation occurs under very practical conditions (DABCO as a catalyst in bulk toluene and open to air) and can be performed with a broad range of each substrate in yields of 36 to 97 %. Importantly, the reaction was found to require the use of acidic additives in combination with the organocatalyst to limit the competitive olefination reaction.     

Enantioselective cyanation/Brook rearrangement/C-acylation reactions of acylsilanes catalyzed by chiral metal alkoxides

New catalytic enantioselective cyanation/1,2-Brook rearrangement/C-acylation reactions of acylsilanes (4) with cyanoformate esters (7) are described. The products of the reaction are fully substituted malonic acid derivatives (8). Catalysts for this transformation were discovered via a directed candidate screen of 96 metal-ligand complexes. Optimization of a (salen)aluminum complex revealed significant remote electronic effects and concentration effects. The scope of the reaction was investigated by using a number of aryl acylsilanes and cyanoformate esters. Chemoselective reduction of the reaction products (8) afforded new enantioenriched alpha-hydroxy-alpha-aryl-beta-amino acid derivatives (32-34) and beta-lactams (35 and 36). This reaction provides a simple method for the construction of new nitrogen-containing enantioenriched chiral building blocks.     

Solid-phase synthesis of 4(1H)-quinolone and pyrimidine derivatives based on a new scaffold-polymer-bound cyclic malonic acid ester

An efficient method for the preparation of polymer-bound cyclic malonic acid ester starting from Merrifield resin has been developed. Reaction of the resin-bound cyclic malonic acid ester with triethyl orthoformate and subsequent double substitution with nucleophilic reagents, such as arylamine, urea, thiourea, 2-aminobenzothiazoles, or isothiosemicarbazones, afforded the corresponding polymer-bound substituted aminomethylene cyclic malonic acid esters, which upon thermal treament led to 4(1H)-quinolones, 3-substituted uracils and thiouracils, 4H-pyrimido[2,1-b]benzothiazol-4-ones, and 1-(N-alkylidene or benzylideneamino)-1,6-dihydro-2-methylthio-6-oxo-pyrimidines, depending on the structures of the nucleophilic reagents.     

Anionic condensations of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4(2)-hydroxybenzaldehydes in the presence of weak bases

Products of the reactions of 4- and 2-hydroxy-3,5-di-tert-butyl-benzaldehydes with malonic acid, diethyl malonate, and acetic anhydride in the presence of weak bases were isolated and identified. The reactions of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with malonic acid and acetic anhydride in the presence of sodium acetate and piperidine gave 3,5-di-tert-butyl-4-hydroxycinnamic acid. The reaction of its 2-hydroxy isomer with acetic anhydride stopped at the stage of formation of the corresponding O-acetyl derivative, while in the reaction with malonic acid the corresponding substituted cinnamic acid and its lactone (coumarin derivative) were formed as intermediate products in a transformation sequence finally leading to 3-(3,5-di-tertbutyl-2-hydroxyphenyl)-3-piperidinopropionic acid and 6,8-di-tert-butyl-2-oxo-3,4-dihydro-2H-chromen-4-ylacetic acid. Analogous differences were typical of reactions of isomeric 4- and 2-hydroxy-3,5-di-tert-butylbenzaldehydes with diethyl malonate. The transformations of the 2-hydroxy isomer were accompanied by hydrolysis and formation of an adduct of intermediate coumarin derivative with diethyl malonate and piperidine.     

Organocatalyzed route to enantioenriched pipecolic esters: decarboxylation of an aminomalonate hemiester

Enantioenriched pipecolic esters were prepared in good yields in the decarboxylation, at room temperature, of N-protected piperidinohemimalonates catalyzed by cinchona alkaloids. Enantiomeric excesses as high as 72% were obtained when using 9-epi-cinchonine and the N-benzoyl substituted piperidinohemimalonate. A detailed study of the different reaction parameters revealed that the selectivity of this noncovalent organocatalyzed reaction is strongly dependent on the solvent, toluene or carbon tetrachloride being the best ones. The whole process based on the malonic acid synthesis was successfully tested on a 10 mmolar scale and established a practical alternative to the asymmetric protonation of lithium enolates.     

新型多重氮杂杯[4]芳烃衍生物的合成

对叔丁基杯[4]芳烃-1,3-二醛基衍生物1与水杨酰肼、烟酰肼、异烟酰肼反应, 合成了具有开链结构新型杯[4]多重氮杂衍生物2a～2c, 产率分别为88%, 85%和90%. 化合物1与乙二酰肼、丙二酰肼、己二酰肼反应, 得到具有桥联结构的新型杯[4]多重氮杂衍生物3a～3c, 产率分别为86%, 89%和90%. 新化合物的结构经元素分析、质谱、核磁共振谱等表征证实, 杯[4]芳烃单元均为1,3-取代且采取锥式构象.     

Synthesis of 4‐hydroxyquinolin‐2(1H)‐one analogues and 2‐substituted quinolone derivatives

A versatile synthetic method for preparing 4‐hydroxyquinolone and 2‐substituted quinolone compounds from simple benzoic acid derivatives was demonstrated. The synthetic strategies involve the use of well known ethyl acetoacetate synthesis, malonic ester synthesis and reductive cyclization. The key intermediates were keto esters 4a‐e , which could be transformed to 4‐hydroxyquinolones 5a,b or 2‐substituted quinolone ethyl esters 6a‐c depending on the reaction conditions. 4‐Hydroxyquinolone analogues were prepared and investigated for N‐methyl‐D‐aspartate (NMDA) activity in vitro. Among these derivatives, 6,7‐difluoro‐3‐nitro‐4‐hydroxyquinolin‐2(1H)‐one ( 9 ) exhibited moderate activity.     

Synthesis of Cinnamic Acid Derivatives Using Ethanol as Solvent or Microwave Assisted Method.

A comparison study about some parameters which influence the condensation of veratraldehyde with malonic acid in the presence of piperidine using ethanol as solvent and microwave irradiation was done, the obtainment of several substituted cinnamic acids are reported.