Application of asymmetric phase-transfer catalysis in the enantioselective synthesis of cis-5-substituted proline esters

A simple, highly stereoselective three-step sequence for the enantioselective synthesis of cis-5-substituted proline esters is described. This sequence features an asymmetric PTC Michael addition, followed by acid catalysed imine exchange and catalytic hydrogenation. Application of this chemistry in the synthesis of the nonpeptide cholecystokinin antagonist (+)-RP-66803 11 is also described.     

Stereoselective synthesis of dihydrofurans under phase-transfer catalyzed conditions

Treatment of cyclic or acyclic -haloenones with various carbon nucleophiles involving active methylene functions afforded the corresponding dihydrofurans in a stereoselective manner with good to high yields. This reaction system can provide a general and practical methodology for the construction of dihydrofuran rings.     

Convenient preparation of tert-butyl esters

A general method is presented for the preparation of tert-butyl esters by the gentle warming of the carboxylic acid in the presence of excess of tert-butyl acetoacetate and a catalytic amount of acid. This method generates only low pressures, and is therefore suitable for laboratory scale pressure glassware.     

Convenient synthesis and anti-proliferative activity of some benzochromenes and chromenotriazolopyrimidines under classical methods and phase transfer catalysis

Abstract

A new series of benzochromene, benzochromenopyrimidine, and benzotriazolopyrimdine derivatives 3-10 were prepared via reaction of ethyl formimidate 2 with primary amines such as sulfanilamide, cyclohexylamine, 3-aminopyridine, 4-aminoantipyrine in addition to its reactions with different acid hydrazides. Compound 5 was further allowed to react with different C-electrophiles by classical and phase transfer catalysis conditions to get novel chromenotriazolopyrimidine derivatives. Screening of the antitumor activity in some of the newly synthesized compounds was tested in vitro against a panel of two human tumor cell lines namely HepG2 and HCT-116 cell lines. Compounds 4, 7, 8, 10, and 20 showed remarkable broad-spectrum antitumor activity.     

Galvinoxyl/K~3Fe(CN)~6/KOH复合体系相转移催化合成对称取代 偶氮苯

用Galvinoxyl自由基为催化剂,芳胺类化合物在饱和铁氰化钾的氢氧化钾溶液和二氯甲烷的两相转移催化下合成了18个对称取代偶氮苯,提供了一个快速、方便、高效的制备偶氮苯类化合物的新方法,讨论了Hammett取代基常数与反应速度的关系,同时也讨论了取代基效应对产率的影响,并对反应机理也做了合理的解释。     

Palladium-catalyzed stereoselective synthesis of E- and Z-1,1-diaryl or triarylolefins

A stereoselective and flexible synthesis of various E- and Z-1,1-diaryl and triarylolefins 3 was achieved from readily available vinylstannanes 1 via stereospecific iodo-destannylation and subsequent palladium-catalyzed Negishi-type cross-coupling reaction with arylzinc reagents under mild conditions.     

Convenient synthesis of enantiopure (R-) and (S-)-3-fluoro-3-aminomethylpyrrolidines

(R-)- and (S-)-3-fluoro-3-aminomethylpyrrolidines were synthesized from methyl α-fluoroacrylate in eight steps. α-Phenylethylamine was used as a chiral auxiliary to separate the racemic mixture. The overall synthesis yield was 31%.     

Synthesis of indan-based unusual alpha-amino acid derivatives under phase-transfer catalysis conditions

Conformationally constrained cyclic alpha-amino acid derivatives were synthesized under solid-liquid phase-transfer catalysis conditions. This methodology involves the bis-alkylation of ethyl isocyanoacetate with various alpha,alpha'-dibromo-o-xylene derivatives [alpha,alpha'-dibromo-o-xylene 5, 2,3-bis(bromomethyl)-1, 4-dimethoxybenzene 6, 1,2-bis(bromomethyl)-4,5-dibromobenzene 7, 2, 3-bis(bromomethyl)naphthalene 8, 1,8-bis(bromomethyl)-naphthalene 9, 6,7-bis(bromomethyl)-2,2-dimethyl-1H-phenalene-1,3(2H)-dione 10, 2, 3-bis(bromomethyl)-1,4-anthraquinone 11, 6, 7-bis(bromomethyl)quinoxaline 12, 3,4-bis(bromomethyl)furan 13, 1,2, 4,5-tetrakis(bromomethyl)benzene 28, and hexakis(bromomethyl)benzene 30] using potassium carbonate as a base and tetrabutylammonium hydrogensulfate as a phase-transfer catalyst to give corresponding isonitrile derivatives, which upon hydrolysis with HCl in ethanol gave amino esters. Using this method electron-deficient as well as electron-rich and halogen-substituted indan-based alpha-amino acids were prepared. The preparation of bis-indan as well as tris-indan alpha-amino esters is also described.     

Regio- and stereoselectivity in the addition reactions of CH-acids to aldehydes under the conditions of phase-transfer catalysis

The regio- and stereoselectivity of the reactions of carbanions, generated from alkanals, carboxylates of the type XYCHCOOEt (X = EtOOC, CN, Ac; Y = H, Br), or derivatives of 3-methyl-4-phosphono-2-butenoic acid using PTC techniques, with aldehydes of various types (alkanals, ,-enals, cross-conjugated enedials, benzaldehydes,etc.) are reviewed. The factors affecting the outcome of these reactions are discussed. The carbanion analogs, triphenylphosphorus ylides, are shown to attack selectively at one of the aldehyde groups of aromatic dialdehydes. The regularities found for the title reactions were used in the syntheses of some biologically active isoprenoids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1867–1885, October, 1995.     

New and efficient conditions for the Z-selective synthesis of unsaturated esters by the Horner-Wadsworth-Emmons olefination

The Horner-Wadsworth-Emmons reaction of both 1 (Still's reagent) and 2 (Ando's reagent) with aldehydes was studied. Tris[2-(2-methoxyethoxy)ethyl]amine (TDA-1) was shown to be an efficient additive when the reaction was performed in THF at −78 °C. Selectivities close to 95% were obtained in the condensation of 1 with aromatic aldehydes. The use of a 5-fold excess of 18C6 in this reaction had already been reported. However, we have defined conditions in which only catalytic amounts are required.     

Convenient synthesis of Z-monoacetates of 2-alkylidene-1,3-propanediols

Various kinds of 3-substituted (Z)-hydroxymethyl-2-propenyl acetates were conveniently obtained in excellent yields by highly regioselective hydrolysis of 2-alkylidene-1,3-propylene diacetates in the presence of 100 w/w % of porcine pancreas lipase (PPL) Type II.     

Reactions of alkyl hetaryl ketones with carbon tetrachloride under liquid/solid phase-transfer catalysis conditions

Summary Reactions of methyl and ethyl hetaryl ketones in the CCl₄/solid KOH system in the presence of 18 crown-6 at room temperature yield the corresponding 2-hetaryl-2-trichloromethyloxiranes in 8–22% yields. Reactions of sterically hindered ketones of the type (hetaryl)COCHR₂ (R = Me, Et) with CCl₄/OH- form the corresponding a-hydroxy ketones of the type (hetaryl)COC(OH)R₂ in 28–44% yields.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 312–315, March, 1994.     

Synthesis of the p-toluenesulfonate of oleyl acohol under conditions of phase-transfer catalysis

The tosylation of oleyl alcohol under the conditions of phase-transfer catalysis has been studied. In this process oleyl p-toluenesulfonate of formed with a yield of up to 80%.Institute of Bioorganic Chemistry, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, 443–445, May–June, 1988.     

New synthesis of t-butyl arylpropiolates using diazo(trimethylsilyl)methylmagnesium bromide

Diazo(trimethylsilyl)methylmagnesium bromide smoothly reacted with t-butyl aryl(oxo)acetates to afford the corresponding arylpropiolates via alkylidenecarbene intermediates. In this reaction system, the magnesium bromide salt of trimethylsilyldiazomethane was significantly efficient compared to the lithium one, commonly known as a reagent for the conversion of aldehydes and aryl ketones into acetylenes.     

Alkylation of hetaryl methyl ketones by propargyl bromide under phase-transfer catalysis conditions

The alkylation of aryl and hetaryl methyl ketones by propargyl bromide using the phase-transfer catalysis system KOH (s)/18-crown-6/benzene is studied. The corresponding C-trialkylated products are selectively obtained in 34–78% yields. Dedicated to Professor Henk van der Plas on his 70th birthday. Latvian Institute of Organic Synthesis, Riga LV-1006, Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 495–497, April, 1999.     

One-pot synthesis of α-diazo-β-hydroxyesters under phase-transfer catalysis and application to the catalytic asymmetric aldol reaction

The one-pot (three steps) synthesis of α-diazo-β-hydroxyesters from tosyl chloride under phase-transfer catalysis is described. The catalytic asymmetric aldol reaction between a diazoester and aldehydes was also investigated and gave moderate to good enantioselectivity.     

Alkylation of some 6-substituted purines under interphase catalysis conditions

The mixture of 9-, 3-, and 7-benzyl-6-substituted purines is formed in almost quantitative yield by the alkylation of 6-benzylamino-, 6-furfurylamino-, 6-methylthio-, and 6-chloropurine with benzyl halides in the biphasic system of the liquid-liquid or liquid-solid type in the presence of interphase catalysts (quaternary ammonium salts, 18-crown-6). The catalytic activity of the quaternary ammonium salts increases with the increase in the lipophilicity of the cation. Taking the alkylation of 6-benzylaminopurine as an example, the possibility of the application of triphasic catalysis in the alkylation reaction of purines is indicated. The alkylation of 6-substituted purines with isopropyl bromide proceeds regioselectively under the conditions of the interphase catalysis with the formation of the corresponding 9-isopropylpurines.For the preliminary communication, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 113–118, January, 1987.