Temperature-sensitive photochemical aromatic substitution on 4-nitroanisole.
A temperature-sensitive photochemical nucleophilic aromatic substitution on 4-nitroanisole by a hydroxide ion in homogeneous solutions, in a two-phase system under phase-transfer catalysis conditions, and in the microwave field is reported. It was found that reaction regioselectivity dramatically changes with temperature in the region of -20 to 196 degrees C. The quantum yield of the 4-methoxyphenol formation was found to be temperature independent, in contrast to that of the 4-nitrophenol formation, suggesting that there is a temperature dependent process occurring after the partitioning between replacement of the nitro group and the methoxy group has taken place. The reaction was also investigated by using quantum chemical calculations. A technique for microwave-assisted photochemical synthesis is proposed as an efficient and practical tool for organic synthesis.
Klán
Petr
P
Department of Organic Chemistry, Faculty of Science, Masaryk University, Kotlarska 2, 611 37 Brno, Czech Republic. klan@sci.muni.cz
Růzicka
Radovan
R
Heger
Dominik
D
Literák
Jaromír
J
Kulhánek
Petr
P
Loupy
André
A