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Title: The investigation and design of palladium catalysed reactions
Author: Gaunt, M. J.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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Chapter 2.2 deals with an investigation of the factors that influence the deprotection of benzyl-type ethers by catalytic hydrogenolysis. Based on these studies it was possible to design the NAP group, a protecting group for the hydroxyl function that can be selectivity removed in the presence of a benzyl ether by hydrogenolysis. Chapter 2.3 describes the application of the NAP group to the protection of carboxylic acids. This group was again removed in the presence of benzyl esters from simple di-carboxylic acid substrates. In more challenging synthetic substrates, where a more enduring benzyl-type group was required, the 4-trifluoromethylbenzyl ester (TFB) was used as a partner to the NAP group. Chapter 2.4 details the development of the TFB group as a new benzyl-type hydroxyl protecting group that is a robust partner for the NAP group in selective debenzylation reactions. Their utility was demonstrated on a selection of carbohydrate examples. Furthermore, a NAP ether was removed in the presence of a TFB ester by hydrogenolysis highlighting the potential power of this protection strategy in synthesis. Chapter 2.5 investigates how the electronic nature of the aromatic ring can affect the regioselectivity of the reductive cleavage of benzylidene acetals. On gluco- and galactopyranoside units an electron rich benzylidene-type acetal is cleaved with DIBAL-H to afford only the 4-OAr product. Conversely, an electron deficient aromatic group leads to the formation of the 6-OAr product under the same conditions.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available