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C(sp(3))-C(sp(2)) cross-coupling reactions are an indispensable tool for organic synthesis. In these reactions transition metals have been extensively employed to promote the formation of valuable carbon-carbon bonds. Herein, we report our recent discovery of a designer thioether as a highly active organocatalyst for reactions between an allyl bromide and an arylboronic acid. The cross-coupling event occurred readily under mild condition in the presence of a weak inorganic base. Preliminary mechanistic studies suggested a sulfonium ylide mechanism.

A highly enantio- and diastereoselective [4+1] annulation between in situ generated ammonium ylides and o-quinone methides for the synthesis of a variety of 2,3-dihydrobenzofurans has been developed. The key factors controlling the reactivity and stereoselectivity were systematically investigated by experimental and computational means and the energy profiles obtained provide a deeper insight into the mechanistic details of this reaction.

Five-membered carbocycles are key structures which are present in a large range of biologically important targets. The development of methodologies for the construction of these systems is thus a fundamental and important issue in organic chemistry. Accordingly, recent years show a growing interest in the development of a (4+1) strategy toward five-membered carbocycles. Most reported (4+1) cycloaddition strategies towards five-membered carbocycles involve addition of carbenes onto 1,3-dienes or vinylketenes. The high reactivity of carbenes is however responsible for a low functional group tolerance. In order to contribute to the development of an effective and general (4+1) annulation strategy, we decided to investigate the reaction between 1,3-diene and sulfur ylide. Indeed, sulfur ylides are known to react as carbenoids. In addition, they are easy to handle and compatible with most functionalities. In the event, we found that sulfonium ylides react with electron poor 1,3-dienes to lead selectively to the corresponding vinylcyclopropanes, with no traces of cyclopentenes. However, we found that rearrangement of these vinylcyclopropanes into cyclopentenes proceeds smoothly in the presence of a catalytic amount of magnesium iodide. A one-pot process of this methodology has been successfully developed. The use of chiral sulfonium ylides allows generating cyclopentenes with excellent enantiomeric excesses., (SC - Sciences) -- UCL, 2016

A new protecting group, 1,2-dimethoxy-4,5-dimethylene, for acyclic amino acid derivatives could be introduced by N,N-dialkylation with 1,2-bis(bromomethyl)-4,5-dimethoxybenzene (1) and removed via amine de-alkylation with acyl chlorides. The method can be used with baseinduced [2,3] and [1,2] Stevens rearrangement products.

A solution of potassium tert-butoxide in THF was shown to remarkably enhance the baseinduced Sommelet–Hauser rearrangement of N-benzylic amino acid-derived ammonium ylides.

The ylide has found practical applications in synthesis for many years, especially in the creation of carbon-carbon double bonds by way of the Wittig reaction. However, this work is concerned with new applications of ylides, especially the unique stabilization powers of phosphorus and nitrogen ylides. While the species reported in this dissertation are fundamentally interesting they are also directed toward synthetically useful applications. The first such species reported herein is the first phosphorus-sulfur bis-ylide, an analog of the well know carbodiposphorane, and has coordination behavior that is similar. This type of species could be a valuable reagent to do tandem olefination and epoxidation reactions on aldehydes or ketones.A major part of this work is directed at using ylides to create stable carbon based ligands for homogeneous catalysis. A stable cyclic(amino)[(bis)ylide] carbene is the first example. The carbenic carbon itself is part of a formal nitrogen ylide, which is further stabilized by one anionic carbon of a phosphorus bis-ylide. The other anionic carbon remains free to coordinate transition metals creating very stable bidentate complexes.The largest portion of this dissertation is focused on the synthesis and ligand behavior of the first stable, fully characterized cyclic vinylidenephosphorane. Once again the special properties of ylides, specifically phosphorus ylides are on display as only one phosphorus stabilizes the low valent carbon center. This new species is a very strong donor for late transition metals, stronger than phosphines and carbenes. As such it is an ideal ligand for numerous catalytic reactions. Two new catalysts using this ligand are made and successfully used in olefin metathesis and hydroamination reactions, respectively.The final portion focuses on the use of N-Heterocyclic Carbenes (NHCs) to stabilize a propadienylidene, a valence isomer of cyclopropenylidene. While the free species alluded synthesis several adducts are

The ylide has found practical applications in synthesis for many years, especially in the creation of carbon-carbon double bonds by way of the Wittig reaction. However, this work is concerned with new applications of ylides, especially the unique stabilization powers of phosphorus and nitrogen ylides. While the species reported in this dissertation are fundamentally interesting they are also directed toward synthetically useful applications. The first such species reported herein is the first phosphorus-sulfur bis-ylide, an analog of the well know carbodiposphorane, and has coordination behavior that is similar. This type of species could be a valuable reagent to do tandem olefination and epoxidation reactions on aldehydes or ketones.A major part of this work is directed at using ylides to create stable carbon based ligands for homogeneous catalysis. A stable cyclic(amino)[(bis)ylide] carbene is the first example. The carbenic carbon itself is part of a formal nitrogen ylide, which is further stabilized by one anionic carbon of a phosphorus bis-ylide. The other anionic carbon remains free to coordinate transition metals creating very stable bidentate complexes.The largest portion of this dissertation is focused on the synthesis and ligand behavior of the first stable, fully characterized cyclic vinylidenephosphorane. Once again the special properties of ylides, specifically phosphorus ylides are on display as only one phosphorus stabilizes the low valent carbon center. This new species is a very strong donor for late transition metals, stronger than phosphines and carbenes. As such it is an ideal ligand for numerous catalytic reactions. Two new catalysts using this ligand are made and successfully used in olefin metathesis and hydroamination reactions, respectively.The final portion focuses on the use of N-Heterocyclic Carbenes (NHCs) to stabilize a propadienylidene, a valence isomer of cyclopropenylidene. While the free species alluded synthesis several adducts are

Herein we wish to report our development of an improved catalyst (S)-(-)-indoline-2-yl-1H-tetrazole (1) for the enantioselective organocatalyzed cyclopropanation of α,β-unsaturated aldehydes with sulfur ylides. The new organocatalyst readily facilitates the enantioselective organocatalytic cyclopropanation, providing cyclized product in excellent diastereoselectivities ranging from 96% to 98% along with enantioselectivities exceeding 99% enantiomeric excess for all reacted α,β-unsaturated aldehydes. The new catalyst provides the best results so far reported for intermolecular enantioselective organocatalyzed cyclopropanation.

Described are the polymerizations of three new dibrominated carbonyl-stabilized yield monomers using copper-bronze in DME to afford polymers that are soluble in common solvents and have unique optical and electronic properties. The first monomer is a zwitterionic N- (butyl)pyrrolinium oxide derivative which, upon polymerization, gives a polymer that has a strong optical absorbance at 520 nm in CCl4. An inter-unit ionic interaction is proposed to explain this large red-shifted band. Bronsted bases and Lewis bases induce a reversible structural change in the polymer to give bathochromic shifts from the visible to the near-IR spectral region. Upon mild reduction of the zwitterionic polymer with Pd/C and H2 (1 atm), some of the extended conjugation is lost, but a polymer forms that has an enormous optical absorption maximum range from the near-UV (290 nm) to the near-IR (886 nm) depending on the solvent or hydroxide concentration. A sample of the reduced polymer can be dispersed in plasticized poly(vinyl chloride). The flexible polymer composite reversibly changes from dark blue-brown in aqueous sodium hydroxide to bright yellow-orange in aqueous HCl. The second monomer, a zwitterionic N-(dodecyl)pyrrolinium oxide derivative, was also synthesized in three steps from pyrrole, and upon polymerization, gives rise to a polymer which also responds reversibly towards Bronsted and Lewis bases. This polymer can be solution cast into flexible-free standing films. jg p.2

Proton abstraction doping has been demonstrated as a viable alternate procedure for the synthesis of electrically conductive polymers through the preparation of poly(phenylene pentadienylene). Additional procedures being used for the synthesis of proton abstraction doping precursors includes sulfur ylide and Grignard condensations, details will be presented. These systems offer tremendous advantages for the study of effects arising from dopant density and conjugation length in organic conductors. One interesting result involves the conductivity of 1,5-diphenypentadiene, a low molecular weight model for poly(p-pheynlene pentadienylene). 1,5-Diphenylpentadienyl anion displays a conductivity of 8S/cm which supports the conclusion that polymeric delocalization of charge is not a necessity.