Asymmetric Allylation of Ketones and Subsequent Tandem Reactions Catalyzed by a Novel Polymer‐Supported Titanium–BINOLate Complex

By using a novel, simple, and convenient synthetic route, enantiopure 6‐ethynyl‐BINOL (BINOL=1,1‐binaphthol) was synthesized and anchored to an azidomethylpolystyrene resin through a copper‐catalyzed alkyne–azide cycloaddition (CuAAC) reaction. The polystyrene (PS)‐supported BINOL ligand was converted into its diisopropoxytitanium derivative in situ and used as a heterogeneous catalyst in the asymmetric allylation of ketones. The catalyst showed good activity and excellent enantioselectivity, typically matching the results obtained in the corresponding homogeneous reaction. The allylation reaction mixture could be submitted to epoxidation by simple treatment with tert‐butyl hydroperoxide (TBHP), and the tandem asymmetric allylation epoxidation process led to a highly enantioenriched epoxy alcohol with two adjacent quaternary centers as a single diastereomer. A tandem asymmetric allylation/Pauson–Khand reaction was also performed, involving simple treatment of the allylation reaction mixture with Co₂(CO)₈/N‐methyl morpholine N‐oxide. This cascade process resulted in the formation of two diastereomeric tricyclic enones in high yields and enantioselectivities.     

Neue Bi(cyclopropylidene) durch CuCl2-katalysierte ‘Carben-Dimerisieiung’ von 1-Bromo-1-lithiocyclopropanen

New Bi(cyclopropylidenes) by CuCl₂-Induced ‘Carbene Dimerization’ of 1-Bromo-1-lithiocycIopropanes A series of so far unknown bi(cyclopropylidenes) 5 are prepared in a simple one-pot reaction by halogenolithio exchange between 1,1-dibromocyclopropanes 1a – c as well as 1e – i and BuLi at ?95°, to give 1-bromo-1-lithiocyclopropanes 2a – c as well as 2e – i , followed by treatment with CuCl₂ at low temperature and a simple workup at room temperature (Table 1). The influence of reaction parameters on yields of 5 (Tables 2, 4, and 5) and diastereoselectivity of the reaction 2 → 5 (Table 3) are discussed. In view of an elucidation of the reaction mechanism, first kinetic experiments of the quantitative reaction 1c → 2c → 5c are reported.     

Fluoroboric Acid Adsorbed on Silica-Gel–Catalyzed Synthesis of 14-Aryl-14H-dibenzo[a,j]xanthene Derivatives

A simple and efficient procedure has been developed for the preparation of 14-aryl-14H-dibenzo[a,j]xanthene derivatives using fluoroboric acid adsorbed on silica gel as a heterogeneous catalyst. The methodology involves the one-pot condensation reaction of β-naphthol and aryl aldehydes under solvent-free conventional heating conditions. The present approach offers several advantages such as shorter reaction times, simple work-up, excellent yields, low cost, and mild reaction conditions. The catalyst is easily recoverable and reusable without loss of its catalytic activity.     

The green synthesis of 2,3-dihydroquinazolin-4(1H)-ones via direct cyclocondensation reaction under catalyst-free conditions

ABSTRACT

A simple and environmentally benign method is described for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones by direct cyclocondensation of 2-aminobenzamide with aromatic aldehydes using water as the reaction medium. The parameters such as temperature, substrate molar ratio and reaction time were examined to establish the optimal synthetic process. The present procedure has advantages of low cost, mild reaction conditions, simple workup process, simply purification, excellent yields and no use of catalyst and hazardous organic solvents.     

An Efficient and Simple Method for Diazotization-Thiocyanation of Aryl Amine using Cross-Linked Poly (4-Vinylpyridine) Supported Thiocyanate Ion

Abstract

An efficient and simple method for the facile synthesis of arylthiocyanates via diazotization-thiocyanation of aryl amines using cross-linked poly (4-vinylpyridine) supported thiocyanate ion is described. Various primary aromatic amines, with electron-withdrawing and electron-donating groups, were transformed into aryl thiocyanates in high to excellent yields in a short reaction time. The present procedure offers advantages such as short reaction time, simple reaction work-up, and the polymeric reagents can also be regenerated and reused for several times without significant loss of their activity.

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.     

Synthesis of a New Library of Pyrano‐phenazine Derivatives via a Novel Three‐Component Protocol

The pyrano‐phenazine derivatives 6 were synthesized by an efficient procedure using the reaction between benzo[a]phenacin‐5‐ols with the condensation product of an aldehyde with Meldrum's acid in the presence of a catalytic amount of Et₃N at ambient temperature. The procedure is very simple, and products could be separated from the reaction media by simple filtration. High functional‐group tolerance both in the benzo[a]phenazin‐5‐ol and aldehyde moieties, facile reaction procedure, medium‐to‐high yields, and simple separation of the products from the reaction media are the advantages of this route.     

A Convenient Method for the Preparation of 1,5‐Diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones

A simple and eco‐friendly method for the preparation of 1,5‐diaryl‐3‐(arylamino)‐1H‐pyrrol‐2(5H)‐ones via the cyclo‐condensation reaction of aldehydes, amines and ethyl pyruvate in the presence of silica supported ferric chloride (SiO₂‐FeCl₃) as reusable heterogeneous catalyst is described. The present methodology offers several advantages such as excellent yields, simple procedure and short reaction times.     

L-proline catalyzed multicomponent domino reaction in polyethyleneglycol-400 for regioselective synthesis of pyrazolyl-tetrahydroindazolones under microwave irradiation

A simple and convenient approach for the synthesis of pyrazolyl-tetrahydroindazolones via L-proline catalyzed three component domino reaction of arylhydrazine, dimedone and pyrazole aldehyde in polyethyleneglycol-400 (PEG-400) under microwave irradiation is described. This novel and green protocol proceeds smoothly in good to excellent yields and provides several advantages such as shorter reaction time, metal-free reaction conditions, simple work-up procedures. Also, recycling of the catalyst and solvent was observed without the loss of activity for three (03) runs.     

Green and highly efficient synthesis of pyranopyrazoles in choline chloride/urea deep eutectic solvent

A simple and efficient multicomponent protocol, using ammonium deep eutectic solvent as a dual catalyst and environmentally benign reaction medium, is developed for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives. This operationally simple protocol does not involve tedious workup or purification, affording the target compounds in short reaction times and excellent yields and avoiding the use of environmentally hazardous solvents and catalysts.     

Immobilization and Continuous Recycling of Photoredox Catalysts in Ionic Liquids for Applications in Batch Reactions and Flow Systems: Catalytic Alkene Isomerization by Using Visible Light

A catalytic (E)‐ to (Z)‐isomerization of olefins using a photoredox catalyst under mild reaction conditions is presented. A variety of (Z)‐alkenes can be prepared in the presence of visible light. A new reaction system allows an easy and efficient scale‐up, as well as a continuous flow process in which the photocatalyst is immobilized in an ionic liquid and continuously recycled by simple phase separation.     

Green,rapid, and highly efficient syntheses of α,α′-bis[(aryl or allyl)idene]cycloalkanones and 2-[(aryl or allyl)idene]-1-indanones as potentially biologic compounds via solvent-free microwave-assisted Claisen–Schmidt condensation catalyzed by MoCl5

A new, green, and highly efficient protocol for the expeditious preparation of some α,α′-bis[(aryl or allyl)idene]cycloalkanones and 2-[(aryl or allyl)idene]-1-indanones via a simple microwave-assisted Claisen–Schmidt condensation reaction catalyzed by MoCl₅ was successfully developed. Outstanding features of the current methodology include the use of solvent-free conditions, simple operation, use of a very inexpensive and available catalyst, low catalyst loading, short reaction times, high yields of the pure products, no harmful by-products, easy workup, and also the applicability of microwave irradiation as a clean source of energy. Furthermore, a gram-scale reaction was successfully conducted, proving the scalability of this current Claisen–Schmidt condensation reaction.     

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

A simple, efficient and green method for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes by a one‐pot condensation reaction of β‐naphthol and aryl aldehydes using silica gel‐supported polyphosphoric acid (PPA/SiO₂), an effective and reusable catalyst, under solvent‐free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy work‐up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.     

Catalyst-free synthesis of novel 4H-indeno[1,2-b]furan-4-ones and furo[2,3-d]pyrimidines in water

An operationally simple, catalyst-free, and efficient protocol for the synthesis of novel 4H-indeno[1,2-b]furan-4-one and furo[2,3-d]pyrimidine derivatives by a one-pot reaction of 2-aminopyridines, 1,3-indandione, or barbituric acid and phenylglyoxal monohydrate in water at reflux, involving domino aldol condensation, Michael addition, and ring-closing reactions is described. This transformation has several advantages, including high yield, short reaction duration, simple workup, and simple purification.     

Variable Time Normalization Analysis: General Graphical Elucidation of Reaction Orders from Concentration Profiles

The recent technological evolution of reaction monitoring techniques has not been paralleled by the development of modern kinetic analyses. The analyses currently used disregard part of the data acquired, thus requiring an increased number of experiments to obtain sufficient kinetic information for a given chemical reaction. Herein, we present a simple graphical analysis method that takes advantage of the data‐rich results provided by modern reaction monitoring tools. This analysis uses a variable normalization of the time scale to enable the visual comparison of entire concentration reaction profiles. As a result, the order in each component of the reaction, as well as k_obs , is determined with just a few experiments using a simple and quick mathematical data treatment. This analysis facilitates the rapid extraction of relevant kinetic information and will be a valuable tool for the study of reaction mechanisms.     

A convenient method for the synthesis of fluorinated α-cyanoacetates via phase-transfer catalysis

A simple and convenient method for the synthesis of fluorinated α-cyanoacetate derivatives has been developed by using electrophilic fluorination of allyl and benzyl substituted α-cyanoacetates with N-fluorobenzensulfonimide (NFSI) as electrophilic fluorinating agent via phase transfer catalysis. The reaction is transition metal free and carried out in aqueous and mild reaction conditions in the presence of readily available tetra-N-butylammonium iodide (TBAI) as phase-transfer catalyst.     

MWCNTs-ZrO2 as a reusable heterogeneous catalyst for the synthesis of N-heterocyclic scaffolds under green reaction medium

A simple, efficient, and facile heterogeneous multi-walled carbon nanotubes-zirconia nanocomposite (MWCNTs-ZrO₂) has been synthesized using natural feedstock coconut juice (água-de-coco do Ceará). The synthesized catalyst was characterized by Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, and X-ray photoelectron spectroscopy analysis. The heterogeneous nanocomposite has been used for one-pot synthesis of various N-heterocyclic compounds like pyrazoles, 1,2-disubstituted benzimidazoles, 2-arylbenzazoles, and 2,3-dihydroquinazolin-4(1H)-ones under green reaction medium at room temperature. This novel method has several advantages, such as short reaction time, simple work-up, excellent yield, and green reaction conditions. The catalyst was recycled up to four times without significant loss in catalytic activity.     

A New Catalyst System for the Heck Reaction of Unreactive Aryl Halides

A simple solution to the age-old problem of the Heck reaction of cheap but unreactive chloro- and bromoarenes [for example, reaction (1)] has been found in the catalyst [Pd(CH₃CN)₂Cl₂]⋅6 Ph₄PCl in the presence of N,N-dimethylglycine as additive. The reaction then proceeds with exceptionally high efficiency.     

Concatenating Suzuki Arylation and Buchwald–Hartwig Amination by A Sequentially Pd-Catalyzed One-Pot Process—Consecutive Three-Component Synthesis of C,N-Diarylated Heterocycles

The concatenation of Suzuki coupling and Buchwald-Hartwig amination in a consecutive multicomponent reaction opens a concise, modular and efficient one-pot approach to diversely functionalized heterocycles, as exemplified for 3,10-diaryl 10H-phenothiazines, 3,9-diaryl 9H-carbazoles, and 1,5-diaryl 1H-indoles, in high yields starting from simple staring materials. Moreover, this one-pot reaction is a sequentially palladium-catalyzed process that does not require additional catalyst loading after the first coupling step.     

Pentafluorophenylammonium triflate as an efficient, environmentally friendly and novel organocatalyst for synthesis of bis-indolyl methane derivatives

A simple, inexpensive, environmentally friendly and efficient route for the synthesis of bis-indolyl methane derivatives by the reaction of indole or N-methyl indole with aldehydes using pentafluorophenylammonium triflate (PFPAT) as a catalyst is described. PFPAT organocatalyst is air-stable, cost-effective, easy to handle, and easily removed from the reaction mixtures.     

ZrCl4/[bmim]BF4‐catalyzed condensation of salicylaldehydes and malononitrile: Single‐step synthesis of 3‐cyanocoumarin derivatives

A versatile and efficient single‐step route to 3‐cyanocoumarins via Knoevenagel condensation of salicylaldehydes and malononitrile using ZrCl₄ as the catalyst (15 mol %) in ionic liquid 1‐(n‐butyl)‐3‐methylimidazolium tetrafluoroborate as reaction medium and catalyst is described. The novel procedure features single step, short reaction time, good yields, and simple workup. J. Heterocyclic Chem., (2011).