Borata Alkene Intermediates for Selective C-C Coupling Reactions

Identificador:  TDX:4437

Handle: https://hdl.handle.net/20.500.11797/TDX4437

Autors:  González Morán, Sara

Resum:
The borata-alkene unit represents stabilized α-monoboryl carbanions, pivotal for new reactions. Advanced synthetic methods and characterization techniques have enhanced our understanding of their properties. This thesis explores the diverse applications of borata-alkene species, enabling the production of novel compounds. Chapter 2 explores Cu(I) complex activation of 1,1,1',1'-tetrapinacolborylethane, yielding α-borylalkyl copper species for allylic alkylation. The structure of 1,1,1',1'-tetrapinacolborylethane is revealed via X-ray diffraction. Reaction conditions are outlined for α-borylalkyl copper species reacting with allyl bromides, yielding mono allylic alkylations via SN2' mechanism. Additionally, homoallyl triboronate systems undergo Cu-catalyzed intramolecular cyclization, favoring trans-diastereoisomer. Chapter 3 unveils regioselective nucleophilic addition of sterically hindered C(sp3) to 1,1-arylboryl alkenes, stabilizing borata-alkene intermediates. Electrophilic trapping of α-boryl carbanionic species with C(sp3) electrophiles is achieved at room temperature, without metal catalysts or radical initiators. This multicomponent reaction forms tetrasubstituted carbons, yielding tertiary boronic esters convertible to novel tertiary alcohols. Chiral substrates result in moderate diastereoisomeric ratios. 11B NMR spectroscopic studies confirm the significance of borata-alkene intermediates, supporting SN2 mechanism. Chapter 4 outlines the exploration of this intermolecular three-component assembly using alkenylboranes as substrate to show that borata-alkene intermediates can react with carbonyl functional groups to synthesize tri- and tetrasubstituted alkenes and dienes. When the borata-alkene interacts with ketones and aldehydes, the resulting α-arylboryl enolates evolve through B-O elimination to generate tri or tetrasubstituted alkenes and dienes, via Boron Wittig sequence. When unhindered α,β-unsaturated carbonyl compounds react with the borata-alkenes, the electrophilic trapping is chemoselectively performed through 1,4-addition generating new tetrasubstituted carbon centers.