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Synthesis of phosphine-alkene ligands and 3-hydroxy piperidines using organolithium chemistry

Haji-Cheteh, Chehasnah (2016) Synthesis of phosphine-alkene ligands and 3-hydroxy piperidines using organolithium chemistry. PhD thesis, University of York.

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Abstract

This thesis describes synthetic routes to P-stereogenic phosphine-alkene ligands and 3-hydroxy piperidines containing heteroaromatics via lithiation-trapping of phosphine boranes or N-Boc pyrrolidine. Both topics are introduced in chapter 1.Chapter 2 presents a route to a new type of P-stereogenic phosphine-alkene ligand B prepared by racemic lithiation of t-butyldimethylphosphine borane or dimethylphenylphosphine borane using s-BuLi. Different allylic halides were used to trap the lithiated intermediate to give chiral alkene-phosphine boranes A. In chapter 3, 3-hydroxy piperidines were synthesised from the ring expansion of hydroxy pyrrolidines. Two novel, short and simple synthetic routes were developed (as shown below). Lithiation-trapping reaction of N-Boc pyrrolidine C using pyridine carboxaldehydes gave N-Boc pyrrolidine alcohols syn-D and anti-D. On the other hand, an alternative approach to obtain 3-hydroxy piperidines anti-H starting from N-trityl prolinal E derived from (S)-proline was investigated. Addition of lithiated heteroaromatics, generated from a Br/Li exchange reaction, to N-trityl prolinal E diastereoselectively gave N-trityl alcohols anti-F. The Boc or trityl deprotection and reductive amination then gave N-benzyl pyrrolidines syn-G and anti-G. Finally, the ring expansion via an aziridinium ion of alcohols syn-G and anti-G gave 3-hydroxy piperidines syn-H and anti-H. The stereochemistry of 3-hydroxy piperidines syn-H and anti-H was proven using J-values in the 1H NMR spectra.

Item Type: Thesis (PhD)
Related URLs:
Academic Units: The University of York > Chemistry (York)
Depositing User: Miss Chehasnah Haji-Cheteh
Date Deposited: 08 Sep 2016 09:56
Last Modified: 31 Aug 2018 00:18
URI: http://etheses.whiterose.ac.uk/id/eprint/13889

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