The invention relates to a crosslinking compound of formula (I) In particular, the present invention relates to a liquid composition comprising a monomer, a (meth)acrylic polymer and at least one crosslinking compound of formula (I). This liquid composition may be used in the form of a syrup and in particular in the form of a syrup for impregnating fibers or fibrous material. The invention also relates to a pseudo-thermoplastic material obtained after polymerization of the liquid composition being at least partially crosslinked. The invention also relates to a process for manufacturing such a liquid composition. The invention also relates to a process for impregnating a long-fiber fibrous substrate with said liquid composition. The invention also relates to a fibrous substrate impregnated with said liquid composition which is useful for manufacturing composite parts. The present invention also relates to a process for manufacturing mechanical parts or structural elements made of composite material and to mechanical parts or structural elements made of composite material obtained via a process using such a liquid composition.