Preparation of unsaturated nitro compounds

Primary aliphatic nitro compounds condense smoothly with aldehydes or ketones. The primary product is usually the nitro compound, whence an unsaturated nitro compound can be obtained by esterification and subsequent removal of the elements of the esterifying acid  

The double bond may, however, be formed during the condensation when aromatic aldehydes are used. 

Dinitro compounds arising by addition of the nitroalkane to the nitroalkene are sometimes formed as by-products. 

Condensing agents are basic catalysts such as alkali carbonates, hydrogen carbonates, hydroxides, or alkoxides, or primary aliphatic amines or calcium hydroxide zinc chloride may also be used with aromatic aldehydes. Ethylene-diamine was introduced by Lerner972 for use in the synthesis of unsaturated nitriles in the aromatic series and he gave a large number of examples in which yields were around 95%. 

Although interaction of an aromatic aldehyde and a primary nitro compound with a primary amine as catalyst leads to the nitro olefin in one step, this need not be the case with other catalysts. 

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