Selective Nitration Of Benzyl Chloride And Its Application In The Synthesis Of Nitrobenzaldehyde

The selective nitration of benzyl chloride and its application in the synthesis of4-nitrobenzaldehyde were studied. Nitration of benzyl chloride with HNO₃ in the presenceof Nb₂O₅(6% weight percent) at 0～5℃for 1.5 hours gave mononitro products in 94%yield with 77～80% para selectivty. Nb₂O₅ was recovered by filtration and reused in thenitration. The yield of mononitro products and para selectivty were above 90% and76%,respectively for 5 times repeated use of Nb₂O₅.Nitration of benzyl chloride with urea nitrate(UN) in H₂SO₄ was also studied. Thenitration was carried out at 25℃for 24 hours and gave mononitro products in 98% yieldwith 90% para selectivty.Base catalyzed hydrolysis of 4-nitrobenzyl chloride at 75～80℃for 22 hours gave4-nitrobenzyl alcohol in 77% yield with 98% purity.Oxidation of 4-nitrobenzyl alcohol in dilute nitric acid at 55℃for 3 hours gave 86%4-nitrobenzaldehyde, compared with industrial oxidation of 4-nitrobenzyl alcohol,whichwas carried out at 70℃for 4 hours and gave 70% 4-nitrobenzaldehyde.4-nitrobenzaldehyde was also obtained in 86% yield with 92% purity via ionic liquidimmobilized TEMPO/CuCl catalyzed oxidation of 4-nitrobenzyl alcohol with molecularoxygen in ionic liquid [bmim]PF₆. The reaction condition is mild,the selectivity is high,and no 4-nitrobenzoic acid is detected in any case.