The mechanism of the first step of the Mitsunobu reaction

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Author(s)
Camp, David
von Itzstein, Mark
Jenkins, Ian D
Year published
2015
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Previous DFT calculations employing phosphine (PH3) and dimethyl azodicarboxylate showed that a cyclic O,N-phosphorane was energetically favored relative to betaine formation. In this study strong experimental support for the formation of the phosphorane is described. The question of whether betaine formation occurs via nucleophilic attack of the phosphine on the azodicarboxylate as has been previously assumed, or via a [4 cycloaddition (cheletropic) reaction to give the O,N-phosphorane, followed by ring-opening to give the betaine has not been resolved. An answer to this intriguing question is provided.Previous DFT calculations employing phosphine (PH3) and dimethyl azodicarboxylate showed that a cyclic O,N-phosphorane was energetically favored relative to betaine formation. In this study strong experimental support for the formation of the phosphorane is described. The question of whether betaine formation occurs via nucleophilic attack of the phosphine on the azodicarboxylate as has been previously assumed, or via a [4 cycloaddition (cheletropic) reaction to give the O,N-phosphorane, followed by ring-opening to give the betaine has not been resolved. An answer to this intriguing question is provided.
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Journal Title
Tetrahedron
Volume
71
Copyright Statement
© 2015 Elsevier. Licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (http://creativecommons.org/licenses/by-nc-nd/4.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, providing that the work is properly cited.
Subject
Medicinal and biomolecular chemistry
Organic chemistry
Physical organic chemistry