Solid-liquid Phase Transfer Catalysis Research Articles

Enantioselective synthesis of both enantiomers of methyl dihydrojasmonate using solid-liquid asymmetric phase-transfer catalysis.

Both enantiomers of methyl dihydrojasmonate (-)-1 and (+)-1 were obtained by a short route using asymmetric Michael addition of dimethyl malonate onto pentyl enone 3, followed by nonracemizing demethoxycarbonylation. The key enantioselective step involves a new system of asymmetric solid-liquid phase-transfer catalysis using solvent-free conditions. Enantiomeric excess as high as 90% (91% yield) was achieved.

Synthesis of cyclopropylamine with phase transfer catalysis

Cyclopropylamine is synthesized with γ-butyrolactone and isopropanol by five steps of ring-opening esterification, cyclization, hydrolysis, acylation and Hofmann degradation. Cyclization and hydrolysis are key steps in the process, and Phase Transfer Catalysis (PTC) is used in the two steps respectively. In the cyclization reaction, because solid-liquid PTC, sodium hydroxide is applied instead of expensive sodium alcoholate, the reaction can be carried out in mild conditions. The optimum reaction conditions are as follows: 0.03:1:1.5 mole ratio of BTEAC to ester to sodium hydroxide, reacting at 50 °C for 2 h with yield of 92%. Hydrolysis of isopropyl cyclopropanecarboxylate is accelerated by liquid-liquid PTC, and the order of catalytic activity is BTEC > BTMAC > CTMAB > TBAB. The results show that the new synthesis method is superior to those from literature and feasible for production with simple routes, mild reaction conditions, cheap materials and total yield of 52.6%.

A Convenient Preparation of Unsymmetrical Ketones from Borinates using Phase Transfer Catalysis

Unsymmetrical ketones were prepared from borinates via the insertion of dichlorocarbene into the C–B bond under solid–liquid phase transfer catalysis conditions and oxidation with alkaline hydrogen peroxide in 50–78% yields.

1-[(2-Acetoxyethoxy)methyl]-3-benzyl-5-bromo-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-ethyl-5-bromo-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-benzyl-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-allyl-5-bromo-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-ethoxycarbonylmethyl-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-methyl-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-methyl-5-bromo-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-ethyl-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-allyl-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

1-[(2-Acetoxyethoxy)methyl]-3-ethoxycarbonylmethyl-5-bromo-6-azauracil

The product 2 was prepared via a direct condensation under solid-liquid phase transfer catalysis (S.L.P.T.C.) [1] conditions.[...]

New chiral didehydroamino acid derivatives from a cyclic glycine template with 3,6-dihydro-2H-1,4-oxazin-2-one structure: applications to the asymmetric synthesis of nonproteinogenic alpha-amino acids.

New chiral (Z)-alpha,beta-didehydroamino acid (DDAA) derivatives with 3,5-dihydro-2H-1,4-oxazin-2-one structure 11a-f have been stereoselectively prepared after condensation of chiral glycine equivalent 7 with aldehydes in the presence of K(2)CO(3) under mild solid-liquid phase-transfer catalysis reaction conditions. These new systems have been used in diastereoselective cyclopropanation reactions using Corey's ylide for the asymmetric synthesis of 1-aminocyclopropane-1-carboxylic acids (ACCs) such as allo-corononamic and allo-norcoronamic acids. The hydrogenation reaction of these systems at ambient pressure in the presence of formaldehyde affords saturated oxazinones and N-methylated oxazinones which have been transformed into the N-methyl-alpha-amino acids (N-MAAs) (S)-2-(methylamino)butanoic acid and (S)-N-methylleucine. In addition, the parent alpha, beta-didehydroalanine derivative 11g has been prepared by a direct aminomethylation-elimination sequence from 7 and Eschenmoser's salt and has been used in Diels-Alder cycloaddition with endo selectivity for the synthesis of the enantiomerically pure bicyclic alpha-amino acids (-)-2-aminobicyclo[2.2.1]heptane-2-carboxylic and (-)-2-aminobicyclo[2.2.2]octane-2-carboxylic acids.

N-Monoalkylation of α-Amino Acid Esters under Solid-Liquid PTC Conditions

N-(2-Nitrophenylsulfonyl)- (o-NBS-AA-OMe, 4) and N-(4-Nitrophenylsulfonyl)-α-amino acid methyl esters (p-NBS-AA-OMe, 5) were N-alkylated with a variety of alkyl halides 6 under solid-liquid phase-transfer catalysis (SL-PTC) conditions, affording the alkylated products o-NBS-N-R2-AA-OMe 7 and p-NBS-N-R2-AA-OMe 8 in excellent yields without any detectable racemization.

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.

Etherification of halo-ester by phase-transfer catalysis in solid–liquid system

In the present study, the kinetics for the etherification of ethyl 2-bromoisobutyrate with potassium 4-benzyloxyphenoxide in the presence of potassium iodide via solid–liquid phase-transfer catalysis (SLPTC) was investigated. The reaction was carried out in a stirred batch reactor. The effects of agitation speeds, concentration of reactants, phase-transfer catalysts, organic solvents, amounts of catalysts, and reaction temperatures were performed to find the appropriate conditions. Using the present reaction system, the hydrolysis side reaction of ether–ester was prevented. A kinetic model taking into account the deactivation behavior of the catalyst was proposed to describe the overall reaction successfully. The pseudo first-order kinetics with the deactivation function was employed to estimate the initial apparent rate constants and the deactivation constants empirically. The activation energies for catalysts tetra- n-butylammonium bromide and tetra- n-phosphonium bromide as well as the behavior of co-catalyst potassium iodide in solid–liquid phase-transfer catalysis were obtained.

An Efficient Synthesis of Polymethylene-bis-Aroyl Thiourea Derivatives under the Condition of Phase Transfer Catalysis

Reaction of polymethylene diamine with aroyl chloride and ammonium thiocyanate under the condition of solid-liquid phase transfer catalysis using polyethylene glycol-400(PEG-400) as the catalyst yielded polymethylene-bis-aroyl thiouiea derivatives 3a -- 3h in good to excellent yield

One-Pot Preparation of Fischer Carbene Complexes by Solid-Liquid Phase Transfer Catalysis

Neutral Fischer carbene complexes bearing alkyloxy groups have been synthesized by direct alkylation of the lithium acylmetalates with alkyl iodides under solid-liquid phase transfer catalysis (PTC).

Phase transfer catalysis: some recent applications in organic synthesis

A survey dealing with the use of anhydrous potassium carbonate as an efficient base for promoting organic reactions under solid–liquid phase transfer catalysis (SL-PTC) conditions is reported. In particular, the generation in situ of trifluoro- and trichloroacetamidide, and reactions of these azaanions with 2-bromocarboxylic esters and epoxides, affording protected α-amino acids and β-amido alcohols, respectively, are described. The reduction of allylic nitroderivatives with CS 2 to oximes or nitriles under SL- and liquid–liquid PTC (LL-PTC) is also presented. Finally, new preparation methods and a study of the reactivity of quaternary onium fluorides, hydrogendifluorides and dihydrogentrifluorides, together with the use of dihydrogentrifluorides as hydrofluorinating agents under SL-PTC conditions, are reported.