Formation of Radicals in the Mitsunobo Reaction
Author(s)
CAMP, D
HANSON, GR
JENKINS, ID
Griffith University Author(s)
Year published
1995
Metadata
Show full item recordAbstract
The first step of the Mitsunobu reaction, involving the reaction of triphenylphosphine with diisopropyl (or diethyl) azodicarboxylate, results in the formation of a radical cation. The EPR spectra of the N-centered radicals reveal hyperfine coupling to two nitrogen nuclei, a phosphorus nucleus, and one or two protons from the alkyl CH (or CH2) groups. The radical is relatively persistent, slowly decomposing at room temperature over a period of about 6 h. When the reaction was carried out in the presence of neopentyl alcohol (1 equiv), the radical still formed. However, in the presence of benzoic acid (1 equiv) or neopentyl ...
View more >The first step of the Mitsunobu reaction, involving the reaction of triphenylphosphine with diisopropyl (or diethyl) azodicarboxylate, results in the formation of a radical cation. The EPR spectra of the N-centered radicals reveal hyperfine coupling to two nitrogen nuclei, a phosphorus nucleus, and one or two protons from the alkyl CH (or CH2) groups. The radical is relatively persistent, slowly decomposing at room temperature over a period of about 6 h. When the reaction was carried out in the presence of neopentyl alcohol (1 equiv), the radical still formed. However, in the presence of benzoic acid (1 equiv) or neopentyl alcohol/benzoic acid, no EPR signal was observed. This suggests that the order of addition of reagents in the Mitsunobu reaction may influence the outcome in some cases. A new mechanism, involving single electron transfer, is proposed for the formation of the Morrison—Brunn—Huisgen betaine.
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View more >The first step of the Mitsunobu reaction, involving the reaction of triphenylphosphine with diisopropyl (or diethyl) azodicarboxylate, results in the formation of a radical cation. The EPR spectra of the N-centered radicals reveal hyperfine coupling to two nitrogen nuclei, a phosphorus nucleus, and one or two protons from the alkyl CH (or CH2) groups. The radical is relatively persistent, slowly decomposing at room temperature over a period of about 6 h. When the reaction was carried out in the presence of neopentyl alcohol (1 equiv), the radical still formed. However, in the presence of benzoic acid (1 equiv) or neopentyl alcohol/benzoic acid, no EPR signal was observed. This suggests that the order of addition of reagents in the Mitsunobu reaction may influence the outcome in some cases. A new mechanism, involving single electron transfer, is proposed for the formation of the Morrison—Brunn—Huisgen betaine.
View less >
Journal Title
Journal of Organic Chemistry
Volume
60
Subject
Chemical sciences
Medicinal and biomolecular chemistry
Organic chemistry