Nitrobenzyl alcohol from nitrobenzaldehyde

Nitrobenzaldehyde has been prepared from />-nitrotoluene by treatment with isoamyl nitrite in the presence of sodium methylate,1 by oxidation with chromyl chloride,2 cerium dioxide,3 or chromium trioxide in the presence of acetic anhydride.4 It can also be prepared by the oxidation of -nitrobenzyl chloride,5 7>-nitrobenzyl alcohol,6 or the esters of -nitrocinnamic acid.7... 

It can also be prepared from -nitrobenzyl alcohol and sodium sulfide,4 by heating -nitrobenzaldehyde with sodium bisulfite 5 and decomposing the addition product with hydrochloric acid, or in low yield by the reduction of />-nitrobenzaldoxime with ammonium sulfide 6 7 and subsequent acid hydrolysis of the amino oxime. 

Fig. 9. Comparison of the spectra of transient interme(diates forme(d during alcohol oxidation (B, C) and aldehyde reduction (D) with the spectrum of the Co(II)E(NAD, triflu-oroethanol) complex (A) in the 450-700 nm region at 25°. (A) Spectra of the Co(II)E (NAD. trifluoroethanol) complex 1, pH 4.3 2, pH 6.23 3, pH 9.0. The spectra shown in (B), (C), and (D) have been selected from RSSF data sets (such as those presented in Figs. 5 and 8) to show the maximum amount of 570 nm intermediate. (B) Oxidation of benzyl alcohol 1, pH 4.8 2, pH 5.6 3, pH 6.8 4, pH 9. (C) Comparison of the transient intermediates formed during the oxidation of (1) 4-nitrobenzyl alcohol, (2) ethanol, and (3) benzyl alcohol, all at pH 9. (D) Comparison of the transient intermediates formed during the oxidation of (1) acetaldehyde, (2) anisaldehyde, (3) benzaldehyde, and (4) 4-nitrobenzaldehyde, all at pH 9. The amplitudes of the spectra have been normalized to the same concentration of Co(II)E. (From Sartorius el al. with permission.) Copyright 1987 American Chemical Society.

The recyclability of the catalyst was demonstrated by using the fluorous phase containing the catalyst several times for further reaction runs. No signifcant decrease in yield and in rate could be observed. For example, even after eight cycles, 86% of analytically pure 4-nitrobenzaldehyde (93% conversion was achieved during the first run) could be obtained from 4-nitrobenzyl alcohol 97). 

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