Full Record

New Search | Similar Records

Author
Title Development of New Biarylphosphane Coinage Metal Complexes for the Regioselective Synthesis of Fused Carbocycles
URL
Publication Date
Date Accessioned
University/Publisher University of Ottawa
Abstract In the last century, no less than five nobel prizes have been awarded for the construction of carbon-carbon bonds : The Grignard reaction (1912), the Diels-Alder reaction (1950), the Wittig reaction (1979), Olefin metathesis (2005) and palladium cross-coupling reactions (2011). The latter two are transition metal catalyzed transformations and their impact on the synthesis of pharmaceutically active compounds, bulk chemicals, fine chemicals, high tech materials as well as agricultural chemicals has been phenomenal. These reactions have changed the way the scientific community views the science of synthesis. Unlike palladium, gold has long been considered to be an expensive and inert metal and therefore, research on Au catalysis was scarse until the begining of the new millenium. Once the scientific community realized the treasure trove of reactivity that gold had to offer, the number of chemical transformations as well as total syntheses involving Au(I)/Au(III) catalysis has sky rocketed. A methodology initially developped by Toste and coworkers has shown that intramolecular addition of a silyl enol ether on alkynes proceeds via a 5-exo¬-dig¬ process. In the first part of this thesis, we will discuss how the ancilary ligand on Au(I) species can influence pathway selectivity for these cyclizations, therefore opening the door to selective 6-endo-dig cyclizations to generate fused carbocycles. With biological processes as well as other competing processes becoming ever more efficient, the future of chemical synthesis is threatened. If it is to survive, the focus of new chemical transformations will have to be on the cost and the greeness of the process. In the second part of this thesis, we will demonstrate how Ag(I) and Cu(I) complexes can offer even better 6-endo-dig¬ selectivity than analogous Au(I) complexes. Silver is about 56 times less expensive than gold, and copper is about 453 times less expensive than gold. Due to the greatly increased selectivity as well as the diminished cost of the catalysts, we have provided access to an attractive 6-endo-dig¬ cyclization process.
Subjects/Keywords Biarylphosphane; Gold catalysis; Silver catalysis; Copper catalysis; 6 endo-dig; 5-exo dig; Carbocycly synthesis
Language en
Country of Publication ca
Record ID handle:10393/23367
Repository ottawa
Date Indexed 2018-01-03
Issued Date 2012-01-01 00:00:00

Sample Search Hits | Sample Images

…Effect of Thermodynamic Bias on the Kinetic Competition between 5-exo and 6endo-dig processes in fully conjugated systems (Modified figure from Alabugin et al. ) ....... 5 Figure 1.4 Relative TS and Product Energies for 5-exo and 6-endo-dig…

…Cyclizations in a Simplified System according to DFT calculations by Alabugin et al. ..................................... 6 Figure 1.5 Literature examples of 5-exo and 6-endo-dig cyclizations that proceed via anionic closurea (modified figure from…

…20 Figure 2.1 Literature examples of Conia-Ene type cyclizations catalyzed by Au(I) .............. 23 Figure 2.2 Proposed Selective Syntheses of Fused Carbocycles Enabled by Selective Conditions for 5-exo-dig and 6-endo-dig Cyclizations…

…Brønsted Acid Catalyzed Addition on to C-C multiple bonds.............................. 1 Scheme 1.2 Effect of annealed ring size on 5-exo-dig vs 6-endo-dig selectivity..................... 8 Scheme 1.3 Looper’s regioselective hydroamination of…

…imply stereoelectronic preference for the exo trajectory over the endo trajectory (Table 1.1).10 Introduction 4 Table 1.1 Obtuse angle of attack on alkynes determined from Alabugin and coworkers’ DTF calculations Cyclization mode Obtuse…

…angle of attack 3-exo 140 4-endo 76 4-exo 133 5-endo 82 5-exo 116 6-endo 99 If one considers the ideal obtuse angle to be 115-130, then the ideal angle of attack should favor 3-exo-dig and 4-exo-dig cyclizations. However, according to…

…intrinsic stereoelectronic preference for the exo cyclizations can be masked by the greater thermodynamic stability of the less strained endo-products. As the ring size increases, the obtuse angle of attack in endo-type cyclizations becomes more favorable…

…and starts to compete with exo-type cyclizations; this is the case for 6-endo-dig processes although 5-exo-dig cyclizations are typically preferred. The later remark brings into context the thermodynamic aspects of these cyclizations. In the case of…

.