Steric versus stereoelectronic control of the facial selectivity in the Diels-Alder reaction

Letourneau, Johnathon E. (1997) Steric versus stereoelectronic control of the facial selectivity in the Diels-Alder reaction. Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (5Mb)

Abstract

The Diels-Alder reactions of 1,2,3,4,5-pentamethyl-1,3-cyclopentadiene and a number of its derivatives, 5-ethyl-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene, 5-methoxymethyl-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene, 5·chloro-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene, 5-bromo-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene and 5-iodo-1,2,3,4,5-pentamethyl-1,3-cyclopentadiene were studied. Additions to these dienes with a number of dienophiles, such as N-phenylmaleimide, 1,4-naphthoquinone, 1,1,2,2-tetracyanoethene, dimethyl acetylenedicarboxylate and 4-phenyl-1,2,4-triazoline-3,5-dione were studied. The results suggest that the facial selectivity of 5-substituted 1,2,3,4,5-pentamethyl-1,3-cyclopentadienes is controlled primarily by steric interactions between the diene and dienophile rather than some stereoelectronic factor. The facial selectivity of 5-alkyl-substituted 1,2,3,4,5-pentamethyl-1,3-cyclopentadienes demonstrated only a slight dependence upon the dienophile used. Differences in facial selectivity for the 5-halo-substituted 1,2,3,4,5-pentamethyl-1,3-cyclopentadienes when different dienophiles were employed have been attributed to electrostatic repulsions between the lone pair electrons of the C-5 substituent and lone pairs on the attacking dienophile. It was observed that dienes such as 5-ethyl-1,2,3,4,S-pentamethyl-1,3-cyclopentadiene and 5-methoxymethyl-1,2,3,4,5- pentamethyl-1,3-cyclopentadiene showed selectivity that demonstrated a large dependence upon the conformation of the substituents on the diene.

Item Type: Thesis (Masters)
URI: http://research.library.mun.ca/id/eprint/10875
Item ID: 10875
Additional Information: Bibliography: leaves 142-143.
Department(s): Science, Faculty of > Chemistry
Date: 1997
Date Type: Submission
Library of Congress Subject Heading: Diels-Alder reaction; Steric hindrance.

Actions (login required)

View Item View Item

Downloads

Downloads per month over the past year

View more statistics