Pedro Mancini

Diels-Alder reactions of N-tosyl-3-nitroindole and dienamides: Synthesis of intermediates of Aspidospermine alkaloids

N -tosyl-3-nitroindole undergoes high yielding Diels-Alder reactions with 1-( N -acyl- N -alkylamino)-1, 3-butadienes in a regioselective manner, to afford advanced intermediates for the synthesis of Aspidospermine alkaloids. Figure options Download full-size image Download as PowerPoint slide

One-step synthesis of 2,9-disubstituted phenanthrenes via Diels–Alder reactions using 1,4-disubstituted naphthalenes as dienophiles

Abstract The normal electron-demand Diels–Alder reaction between 1,4-disubstituted naphthalenes, nitro being one of these two groups, and 1-methoxy-3-trimethylsililoxy-1,3-butadiene gives hydroxyphenanthrene derivatives, the yields being enhanced by placement of more electron-withdrawing groups on the dienophilic system. The nitro group as substituent directs the cycloaddition, and its cis -extrusion as nitrous acid along with the loss of methanol from primary adducts leads to the expected aromatized products.

Nitronaphthalenes as Diels–Alder dienophiles

Abstract 1-Nitronaphthalene, 2-nitronaphthalene and 1,3-dinitronaphthalene react with Danishefsky diene as normal electron demand Diels–Alder dienophiles to give hydroxyphenanthrene derivatives as principal products in reasonable yields. The aromatization is an expected behavior in thermal reactions involving nitro-substituted compounds. However, it was possible to isolate the primary cycloadducts when using 1,3-dinitronaphthalene, although in very low yields. Other less reactive dienes do not undergo cycloaddition.

Reactivity of 1-nitronaphthalene and 1,3-dinitronaphthalene with conjugated dienes. An easy access to N-naphthylpyrroles

1-Nitronaphthalene reacts at high temperature with poor and moderately reactive dienes affording N-naphthylpyrroles while, with the same dienes, 1,3-dinitronaphthalene exhibits the dienophilic character of naphthalenic C3C4 bond producing the corresponding phenanthrenes through a classical Diels–Alder process.

Experimental and theoretical studies on polar Diels–Alder reactions of 1-nitronaphathalene developed in ionic liquids

The reactions between 1-nitronaphthalene 1 and two nucleophilic dienes, Danishefskýs diene 2 and 1-trimethylsilyloxy-1,3-butadiene 3, to yield phenanthrenols 7 and 8 developed in protic and aprotic ionic liquids (ILs) with an imidazolium cation base permit to conclude that the reactions occur in better experimental conditions than in molecular solvents. The yields obtained with protic ILs are better than those observed with aprotic ILs. In this sense, the higher yields obtained with aprotic ILs, (working at 60 °C, 48 h) are comparable with the lower yields observed in protic ILs (60 °C, 24 h). DFT calculations for the reaction of 1-nitronaphthalene 1 with diene 3, in the absence and in the presence of tetrafluoroborate of 1-metilimidazolium [HMIM][BF4] as protic ILs, indicate that this reaction is a domino process that comprises two consecutive processes: i) a polar Diels–Alder (P-DA) reaction between 1 and 3, and ii) an elimination of nitroso acid 5 to yield dihydrophenanthrene 11. Thermodynamic calculations indicate that while the first reaction is the rate-determining step of this domino process, the nitroso acid elimination is the driving force responsible for the formation of dihydrophenanthrene 11. Implicit and explicit solvent effects indicate that while the hydrogen bond formation between HMIM and one oxygen atom of the nitro groups favour the two reactions, implicit solvent effects modelled by PCM decelerate the P-DA reaction by a large solvation of reagents. Finally, DFT analysis of reagents offers an explanation of the catalytic role of protic ILs in these P-DA reactions.

Five-Membered Aromatic Heterocycles in Diels-Alder Cycloadditio Reactions: Theoretical Studies as a Complement of the Experimental Researches

Fil: Brasca, Romina. Universidad Nacional del Litoral; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe; Argentina

Protic and Nonprotic Ionic Liquids in Polar Diels-Alder Reactions Using Properly Substituted Heterocycles and Carbocycles as Dienophiles. A DFT study

The Diels-Alder (D-A) reaction is one of the most useful processes in preparative organic chemistry. Its potential in heterocyclic chemistry and natural products synthesis is very well known. It provides the chemist with one of his best tool for the preparation of cyclic com‐ pounds having a six-membered ring. The process is in one step inter or intramolecular from a diene and dienophile bearing an almost unlimited number of variants. It worth noting that these variants exist not only in the substitution of the reaction component but also in the elec‐ tronic nature of these dienes and dienophiles. (Carruthers W, 1990; Fringelli F. et al 2002)

Ionic Liquids as Binary Mixtures with Selected Molecular Solvents, Reactivity Characterisation and Molecular-Microscopic Properties

This chapter presents the design and analysis of the microscopic features of binary solvent systems formed by ionic liquids, particularly room temperature ionic liquids with molecular solvents. Protic ionic liquids, ethylammonium nitrate and 1-n-butyl-3-methylmidazolium (bmim)-based ILs, were selected considering the differences in their hydrogen-bond donor acidity. The molecular solvents chosen were aprotic polar (acetonitrile, dimethylsulphoxide and N,N-dimethylformide) and protic (different alcohols). The empirical solvatochromic parameters E T N , π*, α and β were employed in order to analyse the behaviour of each binary solvent system. The study focuses on the identification of solvent mixtures of relevant solvating properties to propose them as ‘new solvents’. Kinetic study of aromatic nucleophilic substitution reactions carried out in this type of solvent systems is also presented. On the other hand, this is considered as a new approach on protic ionic liquids. Ethylammonium nitrate can act as both Bronsted acid and/or nucleophile. Two reactions (aromatic nucleophilic substitution and nucleophilic addition to aromatic aldehydes) were considered as model reactions.

A New Highly Selective Chromogenic and Fluorogenic Chemosensor for Copper (II)

Fil: Quindt, Matias Ivan. Universidad Nacional del Litoral. Instituto de Quimica Aplicada del Litoral. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Santa Fe. Instituto de Quimica Aplicada del Litoral.; Argentina

Preparation of Gel Alcohol Flavored with Essential Oils. An Employ of Laboratory Techniques in the Organic Chemistry Study

The main aim of this work is to teach chemistry through a practical application. In it is described a chemical experiment for high school students. They learn fundamental concepts through the preparation of gel alcohol flavored. The experiment has four stages: search information, cultivation of aromatic plants, extraction of essential oils, and elaboration of gel alcohol. The hydro distillation technique was applied in order to obtain the corresponding essential oil. The aromatic plants used were cloves, lavender, rosemary, salvia and cedron. The essential oils were analyzed by gas chromatography. The experiment demonstrated to the students the application of chemistry for the preparation of personal care products making concepts more tangible than a simple reading.