2-Nitrobenzaldehyde

Synthesis

The nitration of benzaldehyde produces mostly 3-nitrobenzaldehyde. Partly for this reason, 2-nitrobenzaldehyde is prepared by indirect routes. The main routes to nitrobenzaldehyde begin with the nitration of styrene or cinnamic acid followed by the conversions of the resulting 2-nitrostyrene and 2-nitrocinnamic acids, respectively. Cinnamaldehyde can also be nitrated in high-yield to 2-nitrocinnamaldehyde. This compound is then oxidized to 2-nitrocinnamic acid, which is decarboxylated to the 2-nitrostyrene. The vinyl group can be oxidized in a number of different ways to yield 2-nitrobenzaldehyde.

2-Nitrotoluene can be oxidized to yield 2-nitrobenzaldehyde.{{cite journal|journal=Acta Chim. Slov.|year=2005|volume=52|pages=460–462|title=Synthesis of 2-Nitrobenzaldehyde from 2-Nitrotoluene|author= Alexander Popkov}} , Alexander Popkov{{cite journal|journal=Org. Synth.|year=1944|volume=24|page=75|doi= 10.15227/orgsyn.024.0075|title= o-Nitrobenzaldehyde|author1=S. M. Tsang |author2=Ernest H. Wood |author3=John R. Johnson}}

Alternatively, 2-nitrotoluene as formed above can be halogenated to a 2-nitrobenzyl halide followed by oxidation with DMSO and sodium bicarbonate to yield 2-nitrobenzaldehyde, which is subsequently purified with the creation of a bisulfite adduct.

Uses

2-Nitrobenzaldehyde is an intermediate in an early route to indigo, a water-insoluble dye commonly used to dye jeans and other fabrics. In the Baeyer–Drewson indigo synthesis, 2-nitrobenzaldehyde condenses with acetone in basic aqueous solution to yield indigo in a one-pot synthesis The method was abandoned in the early part of the 20th century, being replaced by routes from aniline. :[[Image:Baeyer-Drewson indigo synthesis.svg|450px|thumb|left|Baeyer-Drewson Indigo Synthesis]]

Given its two relatively reactive groups, 2-nitrobenzaldehyde is a potential starting material for other compounds. Substituted 2-nitrobenzaldehydes can also be used to yield other important compounds based on indigo, such as indigo carmine.

2-Nitrobenzaldehyde has been shown to be a useful photoremovable protecting group for various functions.

References

References

1. "2-Nitrobenzaldehyde".
2. (2011). "Ullmann's Encyclopedia of Industrial Chemistry".
3. (2011). "Ullmann's Encyclopedia of Industrial Chemistry".
4. Robert E. Buckles, M. Peter Bellis. (1953). "o-Nitrocinnamaldehyde". Org. Synth..
5. (2009-09-01). "Selective aerobic oxidation of styrene to benzaldehyde catalyzed by water-soluble palladium(II) complex in water". Green Chemistry.
6. "Process for the Preparation of 2-Nitrobenzaldehyde".
7. "Indigo Synthesis".
8. "Synthesis of Indigo and Vat Dyeing".
9. (2003-03-11). "Ullmann's Encyclopedia of Industrial Chemistry". Wiley.
10. (2009). "Photochemistry of 2-Nitrobenzylidene Acetals". J. Org. Chem..
11. (2000). "Chemical Actinometry: Using o-Nitrobenzaldehyde to Measure Lamp Intensity in Photochemical Experiments". J. Chem. Educ..