N-halosuccinimide/BF3-H2O, efficient electrophilic halogenating systems for aromatics.
N-Halosuccinimides (NXS, 1) are efficiently activated in trifluoromethanesulfonic acid and BF(3)-H(2)O, allowing the halogenations of deactivated aromatics. Because BF(3)-H(2)O is more economic, easy to prepare, nonoxidizing, and offers sufficiently high acidity (-H(0) approximately 12, only slightly lower than that of trifluoromethanesulfonic acid), an efficient new electrophilic reagent combination of NXS/BF(3)-H(2)O has been developed. DFT calculations at the B3LYP/6-311++G//B3LYP/6-31G level suggest that protonated N-halosuccinimides undergo further protosolvation at higher acidities to reactive superelectrophilic species capable either in the transfer of X(+) from the protonated forms of NXS to the aromatic substrate or in forming a highly reactive and solvated X(+) which would readily react with the aromatic substrates. Structural aspects of the BF(3)-H(2)O complex have also been investigated.
Prakash
G K Surya
GK
Donald P. and Katherine B. Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, USA. gprakash@usc.edu
Mathew
Thomas
T
Hoole
Dushyanthi
D
Esteves
Pierre M
PM
Wang
Qi
Q
Rasul
Golam
G
Olah
George A
GA