Phase Transfer Catalysis Conditions Research Articles

Regioselective nitration of aromatics under phase-transfer catalysis conditions

Abstract Mononitration of aromatics was performed in a two-phase system using phase-transfer catalyst. The most advantageous conditions for the nitration were determined (temperature, reaction time, the type and amount of phase transfer catalyst, nitrification strength of the nitro-sulfuric acid). From the results, a significant improvement in the selectivity and conversion of the nitration of xylene was observed: the ratio of 4-nitro-m-xylene to 2-nitro-m-xylene was unprecedented increased up to 91.3%:7.7%, the ratio of 4-nitro-o-xylene to 3-nitro-o-xylene was also increased to 71.1%:27.2%; both the conversions were over 96%.

ChemInform Abstract: Highly Regio‐ and Diastereoselective Anionic [3 + 2] Cycloaddition under Phase Transfer Catalytic Conditions.

AbstractIn the presence of AMI, the allylic sulfones (Ia) and (IV) undergo highly regio‐ and diastereoselective [3 + 2] cycloaddition with enones to afford trans‐substituted cyclopentenes of type (III)/(VI).

ChemInform Abstract: Microwave Assisted Synthesis, Chemiluminescent and Theoretical Studies of Bromoalkyl Esters of Acridine‐9‐carboxylic Acid.

AbstractPreviously unknown acridine‐9‐carboxylates are synthesized by esterification of acid (I) under microwave irradiation and phase‐transfer catalysis conditions.

L-Proline-Catalyzed Synthesis of Novel 5-(1H-Indol-3-yl-methylene)-thiazolidine-2,4-dione Derivatives as Potential Antihyperglycemic Agents

Knoevenagel condensation between indole-3-aldehyde 1 and an active methylene group containing 2,4-thiazolidinedione 2 in refluxing toluene using L-proline as a catalyst yielded 3, which on alkylation using 2 equivalents of alkylating agent under phase-transfer-catalyzed (PTC) conditions using K2CO3 as a base in dimethylformamide gave N,NI-symmetrically disubstituted 5-(1H-indol-3ylmethylene)-thiazolidine-2,4-diones 4. Alternately, 4 can be synthesized by condensing 5 and 6 in a single step. Using this synthetic strategy, N,NI-unsymmetricallydisubstituted derivatives 9a–f were prepared either by condensing 6 with N-substituted-2,4-thiazolidinedione 5 to obtain 7 followed by alkylation under PTC conditions or condensing 6 with N-unsubstituted- 2,4-thiazolidinedione 2 to yield 8 followed by alkylation under PTC conditions. The latter are the dehydro analogs of the dihydro-N-substituted-5-(1H-indol-3-yl-methylene)-thiazolidine-2,4-diones, which are potential antihyperglycemic agents.

Synthesis and exploration of QSAR model of 2-methyl-3-[2-(2-methylprop-1-en-1-yl)-1H-benzimidazol-1-yl]pyrimido[1,2-a]benzimidazol-4(3H)-one as potential antibacterial agents

Present communication deals with the synthesis of novel 2-methyl-3-[2-(2-methylprop-1-en-1-yl)-1H-benzimidazol-1-yl]pyrimido[1,2-a]benzimidazol-4(3H)-one derivatives under phase transfer catalysis (PTC) conditions using benzyl triethyl ammonium chloride (BTEAC) as PTC. It also elicits the studies on in vitro antimicrobial evaluation of synthesized compounds against a representative genera of gram-negative and gram-positive bacteria i.e., Bacillus subtilis, Staphylococcus aureus, Pseudomonas diminuta and Escherichia coli. All the compounds have been found to manifest profound antimicrobial activity. Moreover, extensive quantitative structure-activity relationship (QSAR) studies have been performed to deduce a correlation between molecular descriptors under consideration and the elicited biological activity. A tri-parametric QSAR model has been generated upon rigorous statistical treatment.

Catalytic Activity of H3PW12O40/Aliquat 336 in Epoxidation of (Z,E,E)-1,5,9-Cyclododecatriene to (E)-1,2-Epoxy-(Z,E)-5,9-Cyclododecadiene

The influence of the technological parameters on the epoxidation of (Z,E,E)-1,5,9-cyclododecatriene (CDT) with 30% hydrogen peroxide to (E)-1,2-epoxy-(Z,E)-5,9-cyclododecadiene (ECDD) was studied under the conditions of phase transfer catalysis (PTC), in the presence of H3PW12O40/Aliquat 336 catalytic system. The parameters considered included stirring speed, the molar ratios of CDT:H2O2 and H2O2:H3PW12O40, temperature, and the nature and concentration of solvent. The variation ranges of these parameters ensuring a high CDT conversion and high selectivity of transformation to ECDD were established. The CDT conversion was 51.4–55.6% and the selectivity of transformation to ECDD was 79.8–95.1%.

A Mild and Efficient Protocol for the Protection of 3-Hydroxychromones Under Phase-Transfer Catalysis

A mild and efficient protocol for the introduction of different protecting groups on 3-hydroxychromones (3-HCs) under phase-transfer catalysis conditions in toluene or dichloromethane/aqueous potassium hydroxide system in the presence of crown ether has been developed. The method is useful for the protection of base-sensitive chromone derivatives. Protected chromones are easier to handle and to purify, and therefore suitable for further chemical transformations. The protecting groups were cleaved cleanly using standard conditions.

A Safe Two-Step Process for Manufacturing Glycidyl Nitrate from Glycidol Involving Solid–Liquid Phase-Transfer Catalysis

A new and safer two-step process for manufacturing glycidyl nitrate from glycidol is reported. In the first step glycidyl tosylate is obtained by reacting glycidol with p-tosyl chloride in the presence of triethylamine according to any one of the well-known procedures for obtaining tosyl esters described in the literature. In the second step, glycidyl tosylate is reacted with NaNO3 in refluxing acetonitrile under solid–liquid phase-transfer catalysis conditions using tetrabutylammonium nitrate as catalyst. Acetonitrile and the phase-transfer catalyst were recycled 12 times without deactivation, yielding 99% pure glycidyl nitrate in a cumulative isolated yield of 81.5% with a catalyst turnover number of 85.7 mol substrate per mol phase-transfer catalyst. This procedure avoids the use of the dangerous reactants used in the current manufacturing processes of glycidyl nitrate and could be useful as a safe and general method for obtaining nitrate esters.

Highly Regio- and Diastereoselective Anionic [3 + 2] Cycloaddition under Phase Transfer Catalytic Conditions

A highly trans and regioselective anionic formal [3 + 2] cycloaddition was achieved with allylic sulfones having an MBH acrylamide backbone under phase transfer organocatalytic conditions giving rise to the formation of unprecedented densely substituted cyclopentene derivatives.

Phase-Transfer Catalyzed Michael Addition Reaction Using a New C2-Symmetric Quaternary Ammonium Salt Derived From l-Proline

A new C2-symmetric quaternary ammonium salt easily prepared from l-proline, was developed and used as an efficient phase-transfer catalyst (PTC) in Michael addition reaction of various active methylene compounds to aromatic enones. Malonate esters and acetylacetone were reacted smoothly with various α, β-unsaturated ketones in good to excellent yields, the reaction conditions were optimized and the substrate scope was also investigated. Thereby, a practical Michael addition methodology was established under phase-transfer catalytic conditions with many advantages, including easy availability of catalyst, mild reaction conditions, short reaction times, simple workup procedures.

Highly Enantioselective Synthesis of α,α-Dialkylmalonates by Phase-Transfer Catalytic Desymmetrization

A novel enantioselective synthetic method for the construction of a quaternary carbon center from malonates via phase-transfer catalytic (PTC) alkylation has been developed. The asymmetric α-alkylation of diphenylmethyl tert-butyl α-alkylmalonates with alkylating agents under phase-transfer catalysis conditions (aq 50% KOH, toluene, 0 °C) in the presence of (S,S)-3,4,5-trifluorophenyl-NAS bromide (8) as PTC catalyst afforded the corresponding α,α-dialkylmalonates in high chemical (up to 99%) and optical yields (up to 97% ee) which could be readily converted to versatile chiral intermediates. Notably, the direct double α-alkylations of diphenylmethyl tert-butyl malonate also provided the corresponding α,α-dialkylmalonates without loss of enantioselectivity. The synthetic potential of this method has been demonstrated by the preparation of α,α-dialkylamino acid and oxindole systems.

Asymmetric Synthesis of α-Methyl-α-Amino Acids via Diastereoselective Alkylation of (1S)-(+)-3-Carene Derived Tricyclic Iminolactone

A novel carene-based alanine-equivalent tricyclic iminolactone 16 has been synthesized via stereoselective dihydroxylation of the double bond, IBX oxidation of the secondary alcohol, esterification of the tertiary alcohol, deprotection of the resulting ester, and subsequent cyclization from commercially available (1S)-(+)-3-carene in 79% overall yield. The iminolactone 16 demonstrated high reactivity toward alkylation with a wide range of electrophiles at room temperature under phase-transfer catalysis conditions. The alkylated products were produced with excellent diastereoselectivities (>98% de) in good isolated yields (86-94%). High yields (83-91%) of optically pure (S)-α-methyl-α-substituted-α-amino acids were obtained by basic hydrolysis of the dialkylated iminolactones with the recovery of the chiral auxiliary 15 (78-87%).

Per-N-methylated analogues of an antitumor bicyclic hexapeptide RA-VII

Penta- N-methyl and hexa- N-methyl analogues of RA-VII, an antitumor bicyclic hexapeptide of plant origin, were prepared. In the former, the nitrogens of d-Ala-1 and Ala-4 and in the latter, those of d-Ala-1, Ala-2, and Ala-4 were methylated under the phase-transfer catalysis conditions. Their solution structures were established by NOESY experiments and the crystal structures by X-ray crystallography. Those two methylated analogues showed much weaker cytotoxicity against P-388 leukemia cells than the parent RA-VII.

Mechanism of formation of 3-methyl derivatives of imidazo[2,1-b]thiazoles and their benzo analogs in the reactions of 2-mercaptoimidazole and 2-mercaptobenzimidazole with 1,3-dichloroacetone under phase-transfer catalysis conditions

The mechanism of the unexpected formation of 3-methyl derivatives of imidazo[2,1-b]thiazoles in the system 2-mercaptoimidazole–1,3-dichloroacetone–solid K2CO3–solid KI–18-crown-6–toluene has been studied. The structure of 3-methyl[1,3]thiazolo[3,2-a]benzimidazole has been confirmed using X-ray structural analysis.

Substituted Quinolinones, Part 14: Synthesis of Novel Dispiro(heterocycle-N,2′-[1,3]dithietane-4′,3″-quinolinedione) Derivatives Under PTC Conditions

The four-membered spiro-heterocycles ethyl cyano(1-methyl-2,4-dioxospiro{1,3-quinoline-3,4′-[1,3]dithietane}-4′-ylidene)-acetate 2a, -malononitrile 2b, -acetylacetone 2c, and thiazetidine isomer 3 were prepared under phase transfer catalysis (PTC) conditions. The thermal treatment of dithietanes 2a–c led to the bis-quinolinyl sulfide 4. Some interesting nucleophilic additions followed by cyclization reactions were carried out with the dithietane 2a to give the corresponding novel dispiro derivatives 5–8, 10–13, and 15.Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.GRAPHICAL ABSTRACT

New and efficient technique for the synthesis of ɛ-caprolactone using KHSO 5 as an oxidising agent in the presence of a phase transfer catalyst

A new method for the synthesis of ɛ-caprolactone based on the Baeyer–Villiger oxidation of cyclohexanone was developed. In the proposed reaction, potassium peroxomonosulphate was used as an oxidising agent under phase transfer catalysis conditions. The effects of the reaction parameters, including the type of phase transfer catalyst, the concentration of the oxidising agent, the type of organic solvent and temperature, were investigated. When dichloromethane was used as an organic solvent and an adequate amount of water was added to the reaction mixture, the highest yield and selectivity for ɛ-caprolactone were achieved at 40 °C.

Convenient preparation of (η 4-alkadiene)dichloroplatinum(II) complexes from [PtCl 6] 2− anions and their reduction to platinum(0) alkene complexes under phase-transfer catalysis conditions

Convenient one-pot reduction-complexation reactions of hexachloroplatinato(IV) anions to (η 4-alkadiene)dichloroplatinum(II) complexes (η 4-alkadiene = COD, DAE, DCPD, NBD) under suitable phase-transfer catalysis conditions are reported. Reduction to zerovalent platinum alkene complexes has been obtained in the presence of an excess of alkene, potassium formate and 18-crown-6 as phase-transfer catalyst (alkene = COD, NB, dba). The crystal and molecular structure of [Pt 1.03(dba) 3]·CH 2Cl 2 has been studied by X-ray diffraction methods: it can be described as a solid solution of Pt(dba) 3 and Pt 2(dba) 3, the mononuclear complex being largely prevailing.

Study of Michael addition on chalcones and or chalcone analogues

Michael addition reaction of 1,3-diphenyl-propenone 1a, e, and f with o-amino thiophenol in the presence of indium trichloride gave the benzothiazine derivatives 2a–c. Condensation of the compound 1a, e with o-phenylene diamine in triethylamine gave the benzodiazepine derivatives 3a–b. Cyclization of 1d with malononitrile in the presence of NaOR/EtOH gave the compound 4. Addition of thiobarbituric acid in triethylamin to 1a gave 5. Condensation of compound 1c with malononitrile in the presence ammonium acetate gave compound 6. 1,3-diphenyl-propenone 1a used as key starting chalcone to react with different active methylene reagents under phase-transfer catalysis condition gave compound 7–9. The structures of the prepared compounds were mainly confirmed on the basis of spectroscopic methods.

Synthesis of 4-cyclo(propyl- and butyl)-1-ethylpyridinium bromides and calculation of their proton and carbon chemical shifts

New 4-cyclo(propyl- and butyl)pyridinium salts have been prepared by alkylation of 4picolinium salt with α,ω-dibromoalkanes under phase-transfer catalysis conditions. The influence of the nature and the catalysis concentration was investigated. The experimentally determined H and C NMR chemical shifts were compared with the values calculated using the GIAO/DFT and HF approach in gas-phase and/or in methanol by using the IEF-PCM method. 1 13

ChemInform Abstract: Alkylating Esterification of 1‐Hydroxy‐3‐phospholene Oxides under Solventless MW Conditions.

1-Alkoxy-3-phospholene 1-oxides were synthesized by the alkylating esterification of the corresponding 1-hydroxy derivatives under phase transfer catalytic, microwave, and solventless conditions using alkyl halides as the reactants and potassium carbonate as the base. In the case of alkylating agents of increased reactivity, there was no need for the use of phase transfer catalyst. Regarding the phosphinic acids, the 3-methyl-3-phospholene oxides were more reactive than the 3,4-dimethyl derivatives. Applying cesium carbonate, isomerization of the 3-phospholene oxide to the 2-phospholene also took place. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:211–214, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20596