2-Nitrobenzylidene diacetate

Reflux the crude p-nitrobenzylidene diacetate with a mixture of 70 ml of ethanol, 70 ml of water and 7 ml of concentrated sulphuric acid for 30 minutes, filter through a fluted filter paper and cool the filtrate in ice. Collect the crystals by suction filtration, wash with cold water and dry in a vacuum desiccator. The yield of p-nitrobenzaldehyde, m.p. 106 °C, is 15 g (55% overall). The spectroscopic characteristics are discussed with those of the ortho isomer, cognate preparation below. 

Cognate preparations. o-Nitrobenzaldehyde. Use 25 g (0.18 mol) of o-nitrotoluene and proceed as for p-nitrobenzaldehyde, but allow a period of 3 hours stirring at 5-10 °C after the addition of the chromium trioxide solution. In the work-up, omit the final ethanol washing to remove unchanged o-nitrotoluene boil the crude product under reflux for 30 minutes with 120 ml of light petroleum (b.p. 60-80 °C). The yield of o-nitrobenzylidene diacetate of m.p. 82-84°C is 16 g (36%). 

Acetal di-Ac [6345-63-7]. 2-Nitrophenyl)methanediol diacetate, 9CI. o-Nitrobenzylidene diacetate. a,a-Diacetoxy-2-nitrotoluene Prisms (ligroin). Mp 90°. 

Three monoacetals, o-,70 wi-97 and p-nitrobenzylidene-dulcitol,97 have been described, the first being formulated, without proof, as the 3,4-derivative. The only triacetal of dulcitol of which we are aware is a tri-(o-nitrobenzylidene)-dulcitol prepared from the aldehyde and the hexitol using as the condensing agent phosphorus pentoxide,70 instead of 75% sulfuric acid which gives the diacetal already mentioned.48 6 Photochemical transformations of o-nitrobenzylidene acetals are discussed on page 148. 

Derivative 61 was synthesized in 71% yield by reductive bond cleavage of the corresponding 4,6-0-o-nitrobenzylidene acetal of methyl 3,4-acetyl- 5-glucoside with triethylsilane and boron trifluoride ether-ate, followed by deacetylation of the 3,4-diacetates with sodium methoxide in methanol. 

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