Stereoselective Synthesis of beta-Hydroxycyclohexanones Using the Anionic Oxy-Cope Rearrangement

Rutherford, Alistair Peter (1999) Stereoselective Synthesis of beta-Hydroxycyclohexanones Using the Anionic Oxy-Cope Rearrangement. PhD thesis, University of Glasgow.

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Abstract

We have developed a method for the rapid and stereoselective synthesis of beta-hydroxycyclohexanones v, using a route that relies on four key reactions as shown below. Substrates for the anionic oxy-Cope (AOC) rearrangement iii were obtained by Takai alkylidenation of aldol products ii derived from alpha,beta-unsaturated aldehydes i. The AOC rearrangement of alcohols iii containing an enol ether was investigated. Conditions were developed that resulted in the formation of cyclohexanones v from alcohols iii in a one-pot process. The stereochemistry of this rearrangement/cyclisation process was investigated. Substrate alcohols iii were found to rearrange predominantly through a chair-like transition state vi, with the potassium counterion chelated to the oxyanion and the enol ether oxygen atom. The acid-catalysed intramolecular aldol reaction of intermediate aldehydes iv was found to result in the preferential formation of an axial hydroxyl group in cyclohexanones v. This result was explained in terms of a stabilising interaction present in intermediate oxonium ion viii, between an axial hydroxyl group and the oxonium ion. The corresponding intermediate with an equatorial hydroxyl group vii, does not contain such an interaction and so is disfavoured. Modelling studies were used to show that this interaction was significant.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Richard Hartley
Keywords: Organic chemistry
Date of Award: 1999
Depositing User: Enlighten Team
Unique ID: glathesis:1999-76202
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 16:29
Last Modified: 19 Nov 2019 16:29
URI: http://theses.gla.ac.uk/id/eprint/76202

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