Development of New Carbon-Carbon Bond-Forming Strategies: Formation and Reactivity of sp³-gem-Organodimetallic Palladium(II)/MRn Alkane Intermediates (MRn=Dialkylalumino, Trialkylstannyl)
MetadataShow full item record
Investigation of the catalytic formation, reactivity and synthetic scope of sp³-gem-organodimetallic palladio(II)/main group metal (main group metal = tributylstannyl, dialkylalumino) alkane species has been carried out. Insight was expanded regarding the inter- and intramolecular reactivity of vinylmetallic reagents in presence of transition metal catalysts. New Pd-catalysed methodologies for carbon-carbon bond formation were developed, such as cyclopropanation of strained olefins, as well as tandem vinylalane arylation/1,2-methyl transfer and 1,2-diarylation. On the one hand, geminal π-allylpalladio(II)/tributylstannylalkane intermediates are produced by oxidative addition of Pd(0) catalysts to α-tributylstannylpropenyl acetate derivatives. They adopt ambiphilic behaviour depending on the transition metal pre-catalyst, presence or absence of phosphine ligands, and reaction temperature. In presence of tetrakis(triphenylphosphine)palladium(0) with additional bidentate ligand, the carbenoid reactivity of these gem-organobismetallic species is exposed by reaction with dimethyl malonate. Deuterium-labeling studies demonstrated sequential functionalisation of the C-Sn and C-Pd bonds. Conversely, phosphine-free catalyst bis(dibenzylideneacetone)palladium(0) uncovers metal-carbene reactivity, and dimerisation and strained alkene cyclopropanation reactions are observed. The nature of the palladium catalyst controls the reactivity of the carbenoid species. Finally, bis(cyclooctadienerhodium(I) chloride) catalytically activates the alkenylstannane moiety, leaving the allylic acetate leaving group available for further transformations. On the other hand, gem-disubstituted trifluoromethanesulfonyloxy- and iodopalladio(II)/ dialkylaluminoneopentane species are generated by intramolecular migratory insertion of 2,2-disubstituted-1-butenyldialkylalanes with σ-arylpalladium(II) triflate and iodide intermediates. Using excess Lewis-basic 1,4-diazabicyclo[2.2.2]octane, electron-rich tris(para-methoxyphenyl)phosphine ligand and acetonitrile as solvent, tandem arylation/1,2-alkyl migration from aluminum to carbon affords 7-substituted-1-ethyl-1-methylindanes containing an all-carbon quaternary stereogenic centre in good yields. This reaction is tolerant of 6-aryl methyl ethers, thioethers and trimethylsilanes. Deuterium labeling established that protiodealumination of the key neopentyl(methyl)aluminum triflate intermediate is caused by the acetonitrile solvent. The organodimetallic species in that study were shown to be configurationally stable, hence the stereospecificity of the process that proceeds via carbopalladation, transmetalation and reductive elimination of an alkylpalladium(II) intermediate. When applied to 1-naphthyl triflate-tethered vinylalanes, the same reaction conditions mediate stereospecific 1,2-diarylation, leading to 2,3,3a,4-tetrahydro-1H-cyclopenta[def]phenanthrenes in excellent yields. The influence of DABCO, tether length and solvent polarity was studied. Selective tandem arylation/1,2-methyl migration could also be achieved in non-polar solvent in absence of Lewis base. While steric properties took precedence over electronic considerations when inducing product selection, preagostic C-H···Pd interactions were postulated to facilitate 1,3-metal migration in the production of 1H-cyclopenta[def]phenanthrene derivatives.
Cite this work
Vincent Hector Emile Trepanier (2006). Development of New Carbon-Carbon Bond-Forming Strategies: Formation and Reactivity of sp³-gem-Organodimetallic Palladium(II)/MRn Alkane Intermediates (MRn=Dialkylalumino, Trialkylstannyl). UWSpace. http://hdl.handle.net/10012/2608
Showing items related by title, author, creator and subject.
Forging links between innovation and sustainability:An empirical examination of the effects on a firm’s financial performance Gabriel, Amir (University of Waterloo, 2016-04-29)Greenhouse gas (GHG) emissions from the North American energy and energy-intensive materials production sectors account for more than 50 percent of total GHG emissions. Based on the argument that CO2 emissions need to be ...
Beaton, Eric (University of Waterloo, 2015-05-22)The modification of benzylic quaternary, tertiary, and secondary carbon centers through Pd-catalyzed hydrogenolysis of Csp3-Csp3 σ bonds is presented. When benzyl Meldrum’s acid derivatives bearing quaternary benzylic ...
Bondarenko, Ganna (University of Waterloo, 2013-02-07)Methods for the modification and functionalization of spᶟ-hybridized carbon centers via cleavage of unstrained carbon-carbon σ bonds are proposed. The bond breaking/forming reactions are promoted by Lewis acids and transition ...