SYNTHESIS AND POLYMERIZATION OF ANTI-BREDT, NITROGEN-BRIDGEHEAD BICYCLIC URETHANES
AuthorEl-Shekeil, Ali Gamaan Salim
AdvisorHall, H. K. Jr.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractThree nitrogen-bridgehead, bicyclic urethanes, 1-aza-8-oxa-bicyclo[4.3.0]nonan-9-one, I, 1-aza-3-oxabicyclo[3.3.1]nonan-2-one, II, and 1-aza-6-oxabicyclo[3.2.1]octan-7-one, III, were synthesized. UNFORMATTED TABLE OR EQUATION OMITTED - PLEASE SEE DISSERTATION. Contrary to popular opinion and in formal disagreement with Bredt's Rule, conformationally strain-free bicyclic urethanes II and III are stable because of N-C=O -O resonance interaction. The demand of the carbonyl for electrons is satisfied by N and O atoms. Urethane II was synthesized by cyclization of 3-chloroformyloxymethylpiperidine hydrotosylate using triethylamine or by refluxing 3-hydroxymethylpiperidinocarbamoyl chloride with excess triethylamine. To satisfy the N-C = 0 and O-C = 0 electron donation, the molecule does not exist in the two-chair form other [3.3.1] systems do, but in a form between the two-chair, boat-chair and flat-chair forms. Its low carbonyl stretching frequency, resistance to hydrolysis and resistance to ring-opening polymerization, all show that the molecule is not strained. 1-Aza-6-oxabicyclo[3.2.1]octan-7-one, III, was synthesized by the reaction of 3-hydroxypiperidinocarbamoyl chloride with four equivalents of triethylamine. It absorbed at 1770 cm⁻¹, 20 cm⁻¹ higher than Ḭ. Water hydrolyzed it at room temperature and phosphoric acid polymerized it at 105°, but it resisted ring-opening polymerization by potassium t-butoxide and p-toluenesulfonic acid in DMSO. As a reference, Ḭ was synthesized in five ways. It was obtained by the action of triethylamine on 2-chloroformyloxymethylpiperidine hydrostosylate, by reacting a mixture of triethylamine. phosgene and 2-hydroxymethylpiperidine, and by refluxing ethylene carbonate, diphenylcarbonate or di-t-butyl tricarbonate with 2-hydroxymethylpiperidine. Urethane I was stable in boiling water for 24 hr, and aqueous sodium hydroxide for two days. It showed no signs of polymerization after heating for extended periods with p-toluenesulfonic acid, phosphoric acid or potassium t-butoxide. The rearrangements of chloroformyloxypiperidines to hydroxypiperidinocarbamoyl chlorides were performed, and unsuccessful attempts were made to synthesize 1-aza-3-oxabicyclo[2.2.2]nonan-2-one.
Degree ProgramGraduate College