Nef Reaction Aldehydes, Ketones, and Carboxylic Acids

The Nef reacdon was originally carried out rmder acidic condidons using strong acid such as aqueous HCl.However, the use of base followed by acid is incompadble v/ithpolyfuncdoniil substrates in addidon, some componnds are prone to undergo side reacdons or fail to react, as discussed in the references. Thus, various modified methods have been devebped, and they 

Sdica gel can be used as an acid for the Nef reacQoa. The basic silica gel impregnated with sodium methoxide has beeu used very couverueully for the Nef reacnou fEq. 6.1)  

In geuer il, the acid-cat ilyzed Nef reacdou is carried out in water or water-coutaining solvents. If the teacdou is carried out in methanol, nitre compounds are coaverted into the correspoadmg dimethylacetals. This process has merits over the coaveadoaa] oae due to the wider applicability of the Nef reacdoa fEq. 6.2).  

The Nef reacdoa is accelerated by the preseace of sdicoa atom at aitro 

The conversion of primary or secondary nitro compounds into aldehydes or ketones is normally accomplished by use of the Nef reaction, which is one of the most important transformations of nitro compounds. Various methods have been introduced forthis transformation (1) treatment of nitronates with acid, (2) oxidation of nitronates, and (3) reduction of nitroalkenes. Although a comprehensive review is available,3 important procedures and improved methods published after this review are presented in this chapter. The Nef reaction after the nitro-aldol (Henry reaction), Michael addition, or Diels-Alder reaction using nitroalkanes or nitroalkenes has been used extensively in organic synthesis of various substrates, including complicated natural products. Some of them are presented in this chapter other examples are presented in the chapters discussing the Henry reaction (Chapter 3), Michael addition (Chapter 4), and Diels-Alder reaction (Chapter 8). 

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