Recent advances in cyanamide chemistry: synthesis and applications

The application of alkyl and aryl substituted cyanamides in synthetic chemistry has diversified multi-fold in recent years. In this review, we discuss recent advances (since 2012) in the chemistry of cyanamides and detail their application in cycloaddition chemistry, aminocyanation reactions, as well as electrophilic cyanide-transfer agents and their unique radical and coordination chemistry

Ruthenium and rhodium catalyzed C-N bond formation reactions in the synthesis of nitrogen containing heterocyclic compounds

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Selenium-mediated allenylation and allylation reactions of N- and O-nucleophiles

Selenium-pi-acid catalysis has been gaining popularity in functionalization reactions of unactivated olefins due to their lower cost and toxicity compared to traditional transition metal catalysts. Some examples of Se-mediated reactions include amination reactions, allylic esterification reactions, and acyloxylation reactions using simple, non-activated olefins. In the first project of this thesis, selenium-pi-acid-catalysis has been used for the functionalization of simple, non-functionalized alkynes. A number of aminoallenes were synthesized from commercially available alkynes using (o-anisyl)2Ph2 as catalyst and NFSI as the source of nucleophile and terminal oxidant. The key feature of this method is that the incorporation of the desired nucleophile and the adjustment of the oxidation state in the final product takes place in a single-step operation. In the second project of this thesis, a new method for the formation of a C-O bond has been described. Allylic phenyl selenides were found to undergo nucleophilic substitution at the selenide with a carboxylic acid nucleophile under irradiation with light of a suitable wavelength. The oxidative activation of the selenide for the substitution reaction is hypothesized to be due to the formation of hydrogen bond networks with the solvent HFIP. The key feature of this method is the chemoselectivity of the reaction and that no extraneous reagent is required for the oxidative activation of the selenium-moiety

Unprecedented Ractivity Of 1-Aza-2-Azoniaallene Salts: New Methodologies And Mechanistic Studies For The Formation Of Diazenium Salts And Tetrahydropyridazines

This thesis describes the research conducted towards the overall goal of developing new synthetic organic methods to facilitate the synthesis of structurally complex nitrogen-containing polycyclic compounds. More specifically, I will describe the diverse reactivity of 1-aza-2-azoniaallene systems to make polycyclic diazenium salts and tetrahydropyridazine rings. I will also describe mechanistic studies undertaken to better understand this reactivity. The Brewer research group has discovered that hydrazones undergo an oxidation reaction with chlorodimethylsulfonium chloride to afford -chloroazo compounds, which react intramolecularly with pendent alkene units to give bicyclic ring fused and bridged diazenium salts. My work includes a mechanistic study to understand how the reaction proceeds and what factors affect its outcome. I will also describe the development of a new method to make diazenium salts in a shorter and more efficient route using a hypervalent Iodine (III) reagent. More recently, our group discovered new and different modes of reactivity of 1-aza-2-azoniaallene salts that included C-H amination reactions, polar [4 + 2] cycloadditions, electrophilic aromatic substitutions, and a chloroamination reaction. Our group was able to utilize these newly discovered reactivities in the preparation of pyrazolines, pyrazoles, tetrahydrocinnolines, and pyridazines, which are all complex compounds of great synthetic utilities that were made in short chemical transformations. Herein I describe my work to understand the scope and limitations of using these heteroallenes in the synthesis of pyridazines

Photoinduced perfluorobutylation of organic substrates in aqueous media

Hydroperfluorobutylation of a series of electron-deficient and electron-rich alkenes through consecutive radical reactions employing perfluorobutyl iodide, n-C4F9I, and (Me3Si)3SiH as chain carrier/hydrogen atom donor is described. The photoinduced Halogen Atom Transfer (HAT) reactions of both olefins and alkynes with n-C4F9I are also shown to be achieved efficiently in aqueous mixtures. On the other hand, aromatic and heteroaromatic substrates can be perfluorobutylated with high efficiency in a photoinduced fashion by means of a Homolytic Aromatic Substitution (SHA) process which involves an Electron Transfer (ET) and a Proton Transfer (PT) step.Fil: Postigo, Jose Alberto. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Stereoselective synthesis of cyclobutanes by contraction of pyrrolidines

Here we report a contractive synthesis of multisubstituted cyclobutanes containing multiple stereocenters from readily accessible pyrrolidines using iodonitrene chemistry. Mediated by a nitrogen extrusion process, the stereospecific synthesis of cyclobutanes involves a radical pathway. Unprecedented unsymmetrical spirocyclobutanes were prepared successfully, and a concise, formal synthesis of the cytotoxic natural product piperarborenine B is reported

A new strategy towards the fawcettimine core of lycopodium alkaloids

A dearomatisation approach to assemble the 6-5-9 fawcettimine core of Lycopodium alkaloids is examined