TY - JOUR
T1 - The Diels - Alder reaction of 4,6-dinitrobenzofuroxan with 1-trimethylsilyloxybuta-1,3-diene
T2 - A case example of a stepwise cycloaddition
AU - Lakhdar, Sami
AU - Terrier, François
AU - Vichard, Dominique
AU - Berionni, Guillaume
AU - Guesmi, Nizar El
AU - Goumont, Régis
AU - Boubaker, Taoufik
PY - 2010/5/17
Y1 - 2010/5/17
N2 - The reaction of 4,6-dinitrobenzofuroxan (DNBF) with 1- trimethylsilyloxybuta-1,3-diene (8) is shown to afford a mixture of [2+4] diastereomeric cycloadducts (10, 11) through stepwise addition-cyclization pathways. Zwitterionic intermediate o-adduct 9, which is involved in the processes, has been successfully characterized by 1H and 13CNMR spectroscopy and UV/ visible spectrophotometry in acetonitrile. A kinetic study has been carried out in this solvent that revealed that the rate of formation of 9 nicely fits the three-parameter equation log k = s (E+N) developed by Mayr to describe the feasibility of nucleophile- electrophile combinations. This significantly adds to the NMR spectroscopic evidence that the overall cycloadditions take place through a stepwise mechanism. The reaction has also been studied in dichloromethane and toluene. In these less polar solvents, the stability of 9 is not sufficient to allow direct characterization by spectroscopic methods, but a kinetic investigation supports the view that stepwise processes are still operating. An informative comparison of our reaction with previous interactions firmly identified as prototype stepwise cycloadditions is made on the basis of the global electrophilicity index, ω, defined by Parr within the density functional theory, and highlighted by Domingo et al. as a powerful tool for understanding Diels - Alder reactions.
AB - The reaction of 4,6-dinitrobenzofuroxan (DNBF) with 1- trimethylsilyloxybuta-1,3-diene (8) is shown to afford a mixture of [2+4] diastereomeric cycloadducts (10, 11) through stepwise addition-cyclization pathways. Zwitterionic intermediate o-adduct 9, which is involved in the processes, has been successfully characterized by 1H and 13CNMR spectroscopy and UV/ visible spectrophotometry in acetonitrile. A kinetic study has been carried out in this solvent that revealed that the rate of formation of 9 nicely fits the three-parameter equation log k = s (E+N) developed by Mayr to describe the feasibility of nucleophile- electrophile combinations. This significantly adds to the NMR spectroscopic evidence that the overall cycloadditions take place through a stepwise mechanism. The reaction has also been studied in dichloromethane and toluene. In these less polar solvents, the stability of 9 is not sufficient to allow direct characterization by spectroscopic methods, but a kinetic investigation supports the view that stepwise processes are still operating. An informative comparison of our reaction with previous interactions firmly identified as prototype stepwise cycloadditions is made on the basis of the global electrophilicity index, ω, defined by Parr within the density functional theory, and highlighted by Domingo et al. as a powerful tool for understanding Diels - Alder reactions.
KW - Cycloaddition
KW - Density functional calculations
KW - Diels - Al-der reactions
KW - Nitrobenzofuroxans
KW - Superelectrophilic heteroaromatics
UR - http://www.scopus.com/inward/record.url?scp=77952250673&partnerID=8YFLogxK
U2 - 10.1002/chem.200903008
DO - 10.1002/chem.200903008
M3 - Article
AN - SCOPUS:77952250673
SN - 0947-6539
VL - 16
SP - 5681
EP - 5690
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 19
ER -