Method for preparing carbene in solution, novel stable form of carbene obtained in particular by means of said method, and uses thereof in catalysis

A process for preparing a catalyst and/or a reactant comprising a carbene and that is stable at 20° C. which is provided in the form of a solution A comprising at least one alcohol and at least one carbine, said process comprising:

• reacting at least one strong base, optionally generated in situ, optionally at a temperature of from 0° C. to 100° C., with at least one compound B which is the precursor of a carbene C, said compound B, which is a salt, comprising an iminium functional group of formula (I):
• with:
• X being chosen selected from the group consisting of:
• O, S, —N(R) and —P(R), with R being a C1-C30 group,
• R1, R2 and R3 being identical or different C1-C30 groups which are optionally substituted and which optionally comprise one or more atoms selected from the group consisting of:
• S, P, Si, N and O,
• X, R1, R2 and R3, taken in pairs, can form a 5-, 6- or 7-membered ring;
• with as following conditions:
• the selecting of said strong base is made so as to be able to carry out a deprotonation of hydrogen of the iminium functional group of structure (I), and
• wherein reacting is carried out in a solvent which is an alcohol or an alcohol mixture.