Phase Transfer Catalysis Conditions Research Articles

Synthesis of 2-substituted 3,4-dihydro- 2H-1,4-benzoxazines through ligandless copper-catalyzed cyclization of hydroxysulfonamides under phase-transfer catalysis conditions

The ring closing under solid–liquid phase-transfer catalysis conditions (SL-PTC) of hydroxysulfonamides 7, bearing a leaving group in the ortho position of the aryl moiety, generates 2-substituted-3,4-dihydro- 2H-1,4-benzoxazines 4 in good to excellent yields. In the case of hydroxysulfonamides 7 bearing a bromine or iodine atom as a leaving group, a copper(I) salt is used to enable the reaction to occur.

Concise Synthesis of Vinylheterocycles through β-Elimination under Solventless Phase Transfer Catalysis Conditions

Various vinylheterocycles compounds have been prepared in excellent yields through β-elimination of the corresponding sulfonate esters with 50% aq NaOH under phase transfer catalysis conditions without organic solvent. The new approach provides an economic and environmentally friendly solution to removal of hazardous bases as well as toxic and expensive dipolar aprotic solvents.

Synthesis, structure and application of a new class of Tr-podands derived in phase-transfer catalysis

Triton X surfactants are used in numerous commercial and industrial products. Large amounts of such surfactants and their various residual biodegradation by-products are ultimately released into the environment. The first synthesis of the group of Tr-polypodands (Triton polypodands), with different central atoms, such as Si, B or P, is reported. Results of this study demonstrate the potential of these compounds in some organic reactions in phase-transfer catalysis (PTC) conditions. The catalytic activity of Triton X ( 1) and Tr-podands ( 2– 8) has been evaluated in an ion promoted reaction under solid–liquid phase-transfer catalysis conditions and compared with that of the earlier studied Si-podands ( 9– 11), used as PTC agents.

Kinetics of halogen-exchange fluorination of 2,6-dichlorobenzaldehyde

Under the conditions of phase transfer catalysis and nitrobenzene as the solvent, the halogen-exchange fluorination of 2,6-dichlorobenzaldehyde using KF as fluorinating agent was studied. The kinetics was investigated and the reaction rate constants were obtained under the optimum conditions of n(KF):n(2,6-dichlorobenzaldehyde): n(Ph4PBr):n(acetone-furan crown ether) = 4:1:0.1:0.05 and temperatures of 433 K, 443 K, 453 K and 463 K. The results illustrated the activation energy of the first and the second step is 4.57 × 104 J·mol−1 and 3.53 × 104 J·mol−1, respectively. The pre-exponential factor is 4.50 × 105 h−1 and 1.08 × 104 h−1, respectively. Thus a reliable kinetics data could be obtained for further research.

Synthesis and biological activity of aryl S-β-glycosides of 1-thio-N-acetylmuramyl-L-alanyl-D-isoglutamine

Phenyl, p-tolyl, and p-tert-butylphenyl beta-1-thio-N-acetylglucosaminides were synthesized by the treatment of thiophenols with peracetate of alpha-D-glucosaminyl chloride in the presence of triethylamine or under the conditions of phase-transfer catalysis with quaternary ammonium salts. The compounds synthesized were used for obtaining of glycosides of 4,6-O-isopropylidene-N-acetylmuramic acid, which were coupled with L-Ala-D-Glu(NH2)-OBzl and then deprotected to obtain the target aryl beta-thioglycosides of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP). The aryl beta-thioglycosides of MDP were found to stimulate an antibacterial resistance toward Staphylococcus aureus in mice. The reliable induction of the spontaneous activity of natural killers in the population of blood mononuclear cells was observed only for phenyl beta-thio-MDP at a dose of 200 microg/ml. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.

Synthesis of 1-(2-aminoethyl)pyrazoles under phase-transfer catalysis

Alkylation of pyrazoles with 2-chloroethylamine was performed under conditions of phasetransfer catalysis. Depending on the substrate acidity, the electrophilic substitution process may be accompanied by dehydrochlorination of the alkylating agent, so that 6 equiv of 2-chloroethylamine should be used in the alkylation of 3,5-dimethylpyrazole.

Synthesis of N-vinylazoles from vinyl acetate without using mercury catalysts

N-Vinyl-substituted pyrazole, 3(5)-methylpyrazole, imidazole, and 1,2,4-triazole were synthesized by addition of the corresponding azoles to vinyl acetate under conditions of phase-transfer catalysis, followed by pyrolysis of N-(1-acetoxyethyl)azoles thus formed at 350–400°C in the presence of water.

2,4-Dibenzoyl-1,3,5-triphenylcyclohexan-1-ol dichloromethane hemisolvate

The asymmetric unit of the title compound, C38H32O3·0.5CH2Cl2, which was synthesized by the reaction of benzaldehyde with acetophenone and NaOH under phase-transfer catalysis and solvent-free conditions, contains two independent mol­ecules of 2,4-dibenzoyl-1,3,5-triphenyl­cyclo­hexan-1-ol and a disordered dichloro­methane mol­ecule. In both independent cyclo­hexa­nol mol­ecules, the central six-membered ring adopts a chair conformation and most of the bulky side groups are located in equatorial positions. The hydroxyl groups are involved in weak intra­molecular hydrogen bonding.

Catalytic Benzoylation of 4-Chloro-3-methylphenol Sodium Salt in Third-Liquid Phase under Conditions of Phase-Transfer Catalysis

In the present study, the benzoylation of 4-chloro-3-methylphenol sodium salt to synthesize 4-chloro-3-methylphenyl benzoate by triliquid phase-transfer catalysis (TL-PTC) was investigated. The third-liquid phase (catalyst phase) can be formed from benzyl tri-n-butylammonium bromide (QBr) reacted with sodium 4-chloro-3-methylphenoxide in the aqueous phase by extra addition of NaCl or NaBr using heptane as the solvent. Before the reaction, about 89% of the catalyst can be concentrated within 1.5 cm 3 of third-liquid phase to make a high catalyst concentration of 1.13 mol/L, which embraces 99.5% of benzyl tri-n-butylammonium 4-chloro-3-methylphenoxide (catalytic intermediate QOR) in the third-liquid phase. The product yield based on benzoyl chloride (limiting reactant) is 98.7% in 30 min of reaction at 20 °C. The reaction rate is strongly dependent on the stirring speed, showing that the interfacial reaction is important. The variations of compositions in the third-liquid phase during the reaction are analyzed. The molar ratio of QOR to Q + in the third-liquid phase remains almost constant after 2 min of reaction, and QOR is not found in the organic phase. The main reaction region locates in the third-liquid phase. The experimental results can be well correlated by pseudo-first-order kinetics. A comparison of product yield under triliquid and liquid-liquid PTC systems shows that TL-PTC offers an effective method for ester synthesis.

Construction of Three Contiguous Tertiary Stereocenters from Aziridines in One Step

A range of active methylene nucleophiles were found to participate in ring-opening of tosylated aziridines under mild phase-transfer catalyzed conditions. High isolated yields coupled with a 1:1 reaction stoichiometry and high levels of relative stereocontrol are distinguishing features of this method. The products are obtained without epimerization, underscoring the optimal conditions afforded by the phase-transfer catalysis for connecting active methylene nucleophiles and weakly electrophilic N-tosylated aziridines.

Synthesis of 2-alkylisoflavones under phase-transfer Catalysis Conditions

2-alkyl isoflavones were synthesised with the aliphatic acid chloride and 2-hydroxydeoxybenzoins under phase-transfer catalysis in acetone–K2CO3 medium involves the modified Baker–VenKataraman transformation

2,4-Dibenzoyl-1-phenyl-3,5-di2-thienylcyclohexanol

The title compound, C34H28O3S2, was synthesized by the reaction of thio­phene-2-carbaldehyde with acetophenone and NaOH under phase-transfer catalysis and solvent-free conditions. The central six-membered ring adopts a chair conformation and all the bulky side groups are located in equatorial positions. The hydroxyl group is involved in weak intra­molecular hydrogen bonding.

Synthesis and Spectroscopic Structural Elucidation of New Quinoxaline Derivatives

A quinoxaline‐2,3‐dione derivative was synthesized, and its chemical structure was determined through spectral analysis. Alkylation of this compound under phase transfer catalysis (PTC) conditions yielded monoalkylated and diakylated adducts. The monolalkylation process was shown to be regioselective occurring on the quinoxalic nitrogen atom rather than on its pyrazolic analogue. The full characterization of the synthesized compounds was studied by concerted use of NMR and MS techniques. Assignments of proton and carbon atoms were achieved through analysis of the 1D 1H and 13C NMR spectra combined with homo‐ and hetero-nuclear 2D NMR experiments. Determination of the alkylation site was achieved through long‐range proton–carbon coupling correlations spectroscopy.

Enantioselective Phase Transfer Catalytic Reactions. A Comparative Study on the Use of Cinchonidine Salts and Glucose-Based Lariat Ethers Including Phosphinoxidomethyl Derivatives

Five model reactions including an epoxidation by alkylhydroperoxide or Darzens condensation, as well as Michael additions were accomplished under phase transfer catalytic conditions using cinchonidine salts or lariat ethers with side arms having HO or Ph2P(O) endgroups as the catalysts. In almost all cases, the use of lariat ethers with either hydroxyalkyl- or phosphinoxido N-substituents led to better enantioselectivities than that of the three cinchonidine derivatives studied.

Sodium dithionite initiated addition of CF 2Br 2 to β-pinene and reactions of the adduct : Synthesis and the reactivity of new 1,1-difluorodienes

Sodium dithionite effectively promotes the addition of dibromodifluoromethane to the exocyclic double bond of β-pinene. The reaction proceeded in a MeCN/H 2O system to give almost quantitatively an adduct, 1-(2-bromo-2,2-difluoroethyl)-4-(2-bromoisopropyl)-cyclohexene, as the sole product. On treatment of the adduct with 2,2,6,6-tetramethylpiperidine elimination of HBr only from the (CH 3) 2CHBr group occurred to give a mixture of regioisomeric dienes, while treatment with 50% KOH under phase transfer catalysis conditions or with K 2CO 3 in DMF resulted in total dehydrobromination to give trienes possessing an exocyclic CH CF 2 group. Surprisingly, the main course of the reactions of the adduct with DBU (1,8-diazabicyclo[5.4.0]undece-7-ene) and also with t-BuOK in THF was elimination of HBr only from the CH 2CF 2Br group to afford 1-(2,2-difluorovinyl)-4-(2-bromoisopropyl)cyclohexene as the main product. Catalytic hydrogenation of the adduct followed by treatment with DBU afforded a conjugated diene, 1-(2,2-difluorovinyl)-4-isopropylcyclohexene. Compounds bearing the CH CF 2 group are new 1,1-difluorodienes which readily reacted with 4-phenyl-3 H-1,2,4-triazoline-3,5-dione to give cycloadducts, derivatives of triazolo[1,2-α]cinnoline.

Convenient Preparation of Chiral α,β‐Epoxy Ketones via Claisen—Schmidt Condensation—Epoxidation Sequence.

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New methodology for the preparation of N-tosyl aziridine-2-carboxylates

N-Tosyl aziridine-2-carboxylate methyl esters were prepared from methyl N-tosyl- l-serinate or N-tosyl- l-threoninate, tosyl chloride, and K 2CO 3, under phase-transfer catalysis (PTC) conditions. The same methodology, as applied to the tert-butyl N-tosyl- l-serine amide, afforded the corresponding newly prepared aziridine-2-carboxamide, as an enantiomerically pure compound.

Phase-transfer catalysis in the chemistry of heterocyclic compounds

Methods for the preparation of heterocyclic systems, the chemical transformations of heterocyclic compounds under conditions of phase-transfer catalysis, and the use of quaternized heterocycles as phase-transfer catalysts are considered.

Efficient and Convenient Synthesis of Diethers from Furoin Under Ultrasound and Solid-liquid Phase Transfer Catalysis Conditions

Efficient and Convenient Synthesis of Diethers from Furoin Under Ultrasound and Solid-liquid Phase Transfer Catalysis Conditions

Synthesis of diethers derived from furoin by phase transfer catalysis under microwave irradiation

A series of new diethers were obtained by alkylation of furoin under microwave irradiation (MWI) in phase transfer catalysis (PTC) conditions. The products of alkyl halides were synthesized in good yields (>75%) within a few minutes, and the products of dihalides were synthesized in fair yields (about 45%). The yields are dramatically improved compared to conventional heating under the same conditions, in spite of similar profiles of rising in temperature.