University of Illinois Urbana-Champaign

Intramolecular Triplex Diels-Alder Reaction With Cyclic Dienes Electron Transfer Induced Nitrogen-Oxygen Bond Cleavage Reactions of N-Aryloxypyridinium and N,n'-Dialkoxybipyridinium Salts

Wolfle, Ingrid

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https://hdl.handle.net/2142/72269

Description

Title
Intramolecular Triplex Diels-Alder Reaction With Cyclic Dienes Electron Transfer Induced Nitrogen-Oxygen Bond Cleavage Reactions of N-Aryloxypyridinium and N,n'-Dialkoxybipyridinium Salts
Author(s)
Wolfle, Ingrid
Issue Date
1992
Doctoral Committee Chair(s)
Schuster, Gary B.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Organic
Abstract
  • Part 1. The intramolecular triplex Diels-Alder reaction of 1-alkenylsubstituted 2,4-cyclohexadienes was investigated with several sensitizers. The (4+2) cycloaddition proceeds in good yield when the dienophile carries a phenyl substituent, but not at all when it is methylsubstituted. For the substrates which have a phenylsubstituted dienophile, cycloaddition proceeds endo-selective and with retention of dienophile stereochemistry. The efficiency of cyclization depends on the length of the tether connecting diene and dienophile. The (4+2) adduct is formed in 88% yield when the tether contains three carbons. When the chain is one carbon longer, dyotropic hydrogen transfer competes with the Diels-Alder cyclization.
  • Part 2. Photoinduced electron transfer to N-(4-cyanophenoxy)pyridinium or N,N$\sp\prime$-diethoxybipyridinium salts results in cleavage of the nitrogen-oxygen bond. The efficiency of this fragmentation process depends crucially on the nature of the departing radical. When a stabilized radical such as 4-cyanophenoxy radical is produced, the rate of bond cleavage exceeds 2 $\times$ 10$\sp $ s$\sp{-1}$. With an unstabilized leaving radical, this rate slows down to ca. 1 $\times$ 10$\sp4$ s$\sp{-1}$.
Graduation Semester
1992
Type of Resource
text
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http://hdl.handle.net/2142/72269

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