(3+2)-Cycloadditions of Levoglucosenone (LGO) with Fluorinated Nitrile Imines Derived from Trifluoroacetonitrile: An Experimental and Computational Study
Grzegorz Mlostoń,
Katarzyna Urbaniak,
Marcin Palusiak,
Zbigniew J. Witczak,
Ernst-Ulrich Würthwein
Affiliations
Grzegorz Mlostoń
Department of Organic & Applied Chemistry, Faculty of Chemistry, University of Lodz, Tamka 12, PL-91-403 Lodz, Poland
Katarzyna Urbaniak
Department of Organic & Applied Chemistry, Faculty of Chemistry, University of Lodz, Tamka 12, PL-91-403 Lodz, Poland
Marcin Palusiak
Department of Physical Chemistry, Faculty of Chemistry, University of Lodz, Pomorska 163/165, PL-90-236 Lodz, Poland
Zbigniew J. Witczak
Department of Pharmaceutical Sciences, Nesbitt School of Pharmacy, Wilkes University, 84 W. South Street, Wilkes-Barre, PA 18766, USA
Ernst-Ulrich Würthwein
Organisch-Chemisches Institut and Center for Multiscale Theory and Computation (CMTC), Universität Münster, Corrensstrasse 40, D-48149 Münster, Germany
The in situ-generated N-aryl nitrile imines derived from trifluoroacetonitrile smoothly undergo (3+2)-cycloadditions onto the enone fragment of the levoglucosenone molecule, yielding the corresponding, five-membered cycloadducts. In contrast to the ‘classic’ C(Ph),N(Ph) nitrile imine, reactions with fluorinated C(CF3),N(Ar) analogues lead to stable pyrazolines in a chemo- and stereoselective manner. Based on the result of X-ray single crystal diffraction analysis, their structures were established as exo-cycloadducts with the location of the N-Ar terminus of the 1,3-dipole at the α-position of the enone moiety. The DFT computation demonstrated that the observed reaction pathway results from the strong dominance of kinetic control over thermodynamic control.
