Surfactants are crystallizing a certain focus for consumer interest, and their market is still expected to grow by 4 to 5% each year. Most of the time these surfactants are of petroleum origin and are not often biodegradable. Cashew Nut Shell Liquid (CNSL) is a promising non-edible renewable resource, directly extracted from the shell of the cashew nut. The interesting structure of CNSL and its components (cardanol, anacardic acid and cardol) lead to the synthesis of biobased surfactants. Indeed, non-ionic, anionic, cationic and zwitterionic surfactants based on CNSL have been reported in the literature. Even now, CNSL is absent or barely mentioned in specialized review or chapters talking about synthetic biobased surfactants. Thus, this review focuses on CNSL as a building block for the synthesis of surfactants. In the first part, it describes and criticizes the synthesis of molecules and in the second part, it compares the efficiency and the properties (CMC, surface tension, kraft temperature, biodegradability) of the obtained products with each other and with commercial ones.

Aiming at the development of green and efficient C–C bond formations (aldol and Mannich reactions), the decarboxylative nucleophilic addition of malonic acid half ester to imines or aldehydes under mild metal-free conditions was studied. A careful control of the temperature and the appropriate choice of the organic base allowed us to obtain β-amino esters or β-hydroxy esters including α-substituted and α,α-disubstituted ones in moderate to excellent yields. ¹H NMR monitoring of the reaction unveiled two distinct mechanisms depending on the hemimalonate used. With the unsubstituted substrate, a carboxylic acid intermediate was isolated upon acid quench resulting from the nucleophilic addition of the putative enol carboxylate anion of the hemimalonate to imines/aldehydes before CO₂ loss. With substituted hemimalonates, the reaction likely involved an enolate which then added to imines/aldehydes or was competitively protonated. According to the base used, the reaction can be carried out either under solvent free-conditions or in an ionic liquid under mild conditions.