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Title: AN ABINITIO STUDY OF A RETRO-WOLFF REARRANGEMENT - FROM DIAZAFULVENONE TO CYANOVINYL ISOCYANATE WITHOUT A SINGLET ALPHA-OXOCARBENE INTERMEDIATE
Authors: Nguyen, Minh Tho ×
HAJNAL, MR
HA, TK
VANQUICKENBORNE, LG
WENTRUP, C #
Issue Date: 1992
Publisher: AMER CHEMICAL SOC
Series Title: Journal of the American Chemical Society vol:114 issue:11 pages:4387-4390
Conference: date:SWISS FED INST TECHNOL,PHYS CHEM LAB,CH-8092 ZURICH,SWITZERLAND; UNIV QUEENSLAND,DEPT CHEM,BRISBANE,QLD 4072,AUSTRALIA
Abstract: Ab initio molecular orbital calculations have been used to study the unimolecular rearrangement of diazafulvenone leading to cyanovinyl isocyanate. The geometries of stationary points were optimized at HF/6-31G** while relative energies were obtained from multireference configuration interaction (MRCISDQ) calculations with the 6-31G** basis set. A singlet oxocarbene structure was not found to be a local minimum but rather a transition structure connecting diazafulvenone to isocyanovinyl isocyanate, the latter molecule being a distinct intermediate during the rearrangement to cyanovinyl isocyanate. Diazafulvenone is calculated to lie 14 and 32 kcal/mol, respectively, above isocyano- and cyanovinyl isocyanate (Z conformers) and to be separated from the isocyanide form by an energy barrier of 44 kcal/mol. The diazafulvenone --> isocyanovinyl isocyanate interconversion, which can be regarded as a retro-Wolff rearrangement, is thus a concerted reaction without a discrete singlet oxocarbene intermediate. It also constitutes the rate-determining step of the entire rearrangement process, in agreement with experimental observation. As shown by an analysis of localized orbitals, the diazafulvenone --> isocyanovinyl isocyanate interconversion involves six electron pairs that circulate following a cyclic motion.
ISSN: 0002-7863
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Quantum Chemistry and Physical Chemistry Section
× corresponding author
# (joint) last author

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