Diastereoselectivity of the metallo-enamine condensation; addition and cyclization reactions of vinyl isocyanates

The diastereoselectivity of the metallo-enamine condensation was examined using a variety of imines and aldehydes. The highest selectivity (5:95, anti:syn) was observed in the reaction of the lithium enamine of propylidene-t-butylamine with pivaldehyde. Therefore, high diastereoselectivities can be achieved through the use of aldehyde derivatives, although with lithium, sterically hindered substituents on both the imine nitrogen and on the aldehyde are required. A non-chelated transition state is proposed to account for the formation of the syn product from the ($E$)-metallo-enamine. Reduction of the intermediate alkoxide was developed as a way to prepare 1,3-amino alcohols and to avoid the risk of epimerization of the hydroxy imines. The use of other metals was examined. Titanium provided high levels of syn selectivity in all reactions ($<$10:90 in most cases), regardless of the size of the substituents although the yields were moderate (20-66%). An octahedral titanium complex is invoked to explain the observed results. Metallo-enamine condensations with zirconium, zinc, boron, and tin were nonselective. Hauser's work on the condensations of amide enolate anions with aldehydes was repeated and was found to be in error owing to the solubility of the minor isomer in the aqueous phase. The reactions were not exclusively anti selective, as reported, but instead provided hydroxy amides in ratios of 63:37 and 78:22. Imidate anions were also nonselective.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Chemistry

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2011

Author dc:creator

• Wolk, Diane Ridout

Contributors dc:contributor

• Coates, Robert M.

• Chemistry, Organic

Statement dc:rights

• Copyright 1990 Wolk, Diane Ridout

Language dc:language

eng

Identifier

AAI9026354
(UMI)AAI9026354

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/21192