Reinventing Aromatic Substitution: A Novel Look

<p>Electrophilic aromatic substitution (EAS) and directed <em>ortho</em>-metalation (DoM) involve the direct substitution of an arene hydrogen. A major drawback involving EAS is the necessity for harsh forcing conditions for the reaction to proceed. Catalysts such as Lewis acids FeBr₃ and AICI₃ for the introduction of halogens and acyl groups, respectively, are each highly toxic and corrosive. Textbook preparations of aryl iodides classicaly involved the use of iodine and nitric acid. This approach affords only modest yields and does not provide regiospecific substitution of most substituted aromatics because most contain <em>ortho</em>/<em>para</em> directors which afford mixtures of isomers. The novelty of our procedure for the synthesis of the iodinated aromatics is twofold in that regiospecific <em>para</em>-iodination is observed and hydrocarbon media are utilized. Hydrocarbon media are less hazardous and greener than media used for halogenations reported in literature. This procedure always yields derivatives regiospecifically substituted para to an electron donating substituent. Moreover, this method eliminates the need to use hazardous oxidative catalysts. DoM is a reaction regiospecifically substitute an arene hydrogen at the <em>ortho</em> position. The media used in DoM reactions are less hazardous than those required for a variety of EAS reactions. The only problem for this reaction is use of extremely strong bases, alkyllithium reagents, which are known to be air and water sensitive. However, the DoM reaction does eliminate the need to separate <em>ortho</em>/<em>para</em> isomer mixtures so that only a single product is generated. The metalation yields predominantly products regiospecifically substituted <em>ortho</em>-to the direcing metalating group (DMG). With our deficiency catalysis concept and subsequent purificaion methods, relatively pure <em>ortho</em>-lithiated intermediates have been prepared. The study of catalysts/promoters on the derivatization of these intermediates is anticipated to be extremely insightful. For this study, we have shown that highly selective, efficient ortho-lithiation can be achieved by deficiency catalysis utilizing <em>n</em>-BuLi as the only strong metalating base.</p>

Name thesis:degree_name

Master of Science

Discipline thesis:degree_discipline

Department of Chemistry

Year

2013

Author dc:creator

• Nguyen, Quang

Contributors dc:contributor

• Donald W. Slocum (Director), Cathleen Webb, Rajalingam Dakshinamurthy

• Electrophilic Aromatic Substitution
• Directed Ortho Metalation
• Chemical Reactions
• Analytical Chemistry
• Chemistry
• Organic Chemistry

Repository record dc:identifier

https://digitalcommons.wku.edu/theses/1292

OAI identifier oai:identifier

oai:digitalcommons.wku.edu:theses-2295