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A theoretical and experimental study of the polar Diels–Alder cycloaddition of cyclopentadiene with nitrobenzodifuroxan
Author(s) -
Steglenko Dmitry V.,
Kletsky Mikhail E.,
Kurbatov Sergey V.,
Tatarov Artem V.,
Minkin Vladimir I.,
Goumont Régis,
Terrier François
Publication year - 2009
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1469
Subject(s) - chemistry , cycloaddition , cyclopentadiene , adduct , reactivity (psychology) , context (archaeology) , electrophile , density functional theory , computational chemistry , diels–alder reaction , polar , pericyclic reaction , stereochemistry , medicinal chemistry , organic chemistry , catalysis , medicine , paleontology , physics , alternative medicine , pathology , astronomy , biology
The mechanism of the Diels–Alder interaction of 4‐nitrobenzodifuroxan (NBDF) with cyclopentadiene (Cp), resulting in the highly stereoselective formation of the stable endo [2+4] adduct has been elucidated by combining density functional theory (DFT) and experimental studies. Calculations at the B3LYP/6‐31G* level reveal that this adduct does not derive from a direct normal electron demand cycloaddition process. Instead, the evidence is that the interaction proceeds initially through a very polar inverse electron demand process to afford the intermediate [4+2] cycloadduct. Then, this species undergoes a complete conversion into the more stable isomeric endo [2+4] adduct via a [3+3] Claisen‐type sigmatropic shift. The lifetime of the [4+2] intermediate was sufficient to allow its full 1 H NMR characterization at −10 °C. Viewing the results in the general context of the Diels–Alder reactivity of nitrobenzofuroxans, a noteworthy feature is that the similar behavior of NBDF and 4‐aza‐6‐nitrobenzofuroxan (ANBF) goes along with a similar positioning of the two compounds on the general electrophilicity scale of Parr et al . Copyright © 2008 John Wiley & Sons, Ltd.