Item – Theses Canada

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OCLC number
46561332
Link(s) to full text
LAC copy
LAC copy
Author
Ma, Jihai,1964-
Title
Mono(trimethylsilyl) bisketenes : cycloaddition and electrophilic addition reactions.
Degree
Ph. D. -- University of Toronto, 1997
Publisher
Ottawa : National Library of Canada = Bibliothèque nationale du Canada, [1998]
Description
3 microfiches.
Notes
Includes bibliographical references.
Abstract
The 1,2-bisketenes 2-phenyl-3-trimethylsilyl-1,3-butadiene-1,4-dione and 2,3-di-tert-butyl-1,3-butadiene-1,4-dione were generated by photolysis of the corresponding cyclobutenediones in yields of 87-99%, and 5-15%, respectively, as relatively long-lived intermediates at room temperature. The 2-ethoxy-3-trimethylsilyl 1,2-bisketene generated similarly was only observed as a transient species by time resolved infared spectroscopy. These bisketenes were not stable at high temperature and reformed the cyclobutenediones. 3,4-Di-tert-butylcyclobutenedione was also prepared by dehydrochlorination of the corresponding succinyl chloride at high temperature. The reactions of 1,2-bisketenes with nucleophiles such as alcohols and amines were studied and the reactions were found to go by stepwise processes, and in some cases the monoketene formed could be observed and even isolated. The reactions of bisketenes with electrophiles were studied. The reaction of 2,3-bis(trimethylsilyl)-1,3-butadiene-1,4-dione with bromine was found to occur by attack at C$\sb\alpha$ and resulted in a 1,4-addition. This 2,3-bis(trimethylsilyl) bisketene was also found to react with t-BuCl to give a monoalkyl substituted bisketene. Cycloaddition reactions of some 1,2-bisketenes were also studied, and those were found not to give Diels-Alder reactions with various dienophiles. 2,3-Bis(trimethylsilyl)-1,3-butadiene-1,4-dione was found to react with acetaldehyde give a ketenyl lactone which upon heating gave a vinyl ketene after loss of CO$\sb2$. The more reactive 2-phenyl-3-trimethylsilyl-1,3-butadiene-1,4-dione was found to react with electron-rich alkynes to give furanone derivatives under photolysis conditions or heating. With the reactive alkyne ethoxytrimethylsilylethyne 4+2 cycloaddition to form a benzoquinone was the major pathway. The reaction of bisketenes with diazo compounds gave furanone and cyclopentene-3,5-dione derivatives.
ISBN
0612280039
9780612280038