The Development of the Akynyl Heck Reaction Towards the Synthesis of Allenes

Date
2017
Authors
Neff, Robynne K.
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Abstract

The following dissertation will highlight two main novel synthetic pathways for the preparation of highly functionalized substituted allenes. Allenes have been recognized for their diverse incorporation into natural products, over 150 to date, and display a myriad of different biological activities. Allenes also enjoy a unique niche as a functional group in organic chemistry. Their orthogonal cumulative π-systems provide complementary yet, in some cases, distinct reactivity compared to their alkene and alkyne cousins. Moreover, their ability to possess axial chirality sets them apart from all other functional groups. Particularly of interest is the ability to transfer the allene’s axial chirality into new stereogenic centers. This dissertation will highlight our ability to exploit palladium-catalyzed β-hydride eliminations towards the construction of highly enantioenriched allenes. The initial basis of this discovery is the ability to access cationic vinyl PdII intermediates that undergo facile β-hydride eliminations from readily available enol triflates. Secondly, this dissertation will demonstrate the extension of this discovery to a spin on the Nobel prize winning methodology, the alkynyl Heck reaction for the development of tri- and tetrasubstituted allenes. During the optimization of the latter, it became necessary to undertake catalyst development. This dissertation will disclose the development of BobCat (C50H53Na2O6PPd), a new Pd(0)-complex with an ionizable dba ligand that undergoes complete dissociation under biphasic basic conditions to form the “activated” homoleptic catalysts.

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Keywords
allene, asymmetric catalysis, axial chirality, beta hydride elimination, palladium catalysis
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Department
Chemistry