|
Abstract
|
Silica supported boron trifluoride, BF3.SiO2, which is easy to prepare, shows unusually high acidity
which can be controlled by activation temperature, and exhibits considerable catalytic activity,1
enables better accessibility of the reactants to the active sites. The BF3.SiO2 is used in several organic
transformations, such as in Claisen-Schmidt condensations,2 in syntheses of 14-aryl or alkyl-14Hdibenzo[
a,j]xanthenes,3 1,2,4,5-tetrasubstituted imidazoles 4, tetrahydrobenzo[a]xanthenes-11-one,5 in
the polymerization of styrene,6 the preparation of polyfunctionalized piperidin-4-ones,7 α-amino
phosphonates,8 quinoxalines,9 and 3,4-dihydropyrimidin-2(1H)-ones.10 Among the polyfunctionalized
benzene compounds, the substituted-2,6-dicyanoaniline system acquires important biological
properties11 but also serves as a key precursor for the construction of bioactive heterocycles.12 We
report a simple method for the synthesis of 3,5-disubstituted-2,6-dicyanoaniline derivatives via onepot
cascade annulation of nitro-olefin, malononitrile and aldehydes in the presence of a catalytic
amounts silica supported boron trifluoride (Scheme 1).
|