Method for preparing nitrogenous compounds of formula: wherein - R 1 represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocycle, a carbonyl group (-CO-), a silylated group, a siloxy group, an amino group, said alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocycle, silylated, siloxy and amino groups being optionally substituted, - R 1 optionally comprises an H, C, N, O, F, Si and/or S as defined below; - H represents a hydrogen atom ( 1 H), deuterium ( 2 H) or tritium ( 3 H); - C represents a carbon atom ( 12 C), an isotope 11 C, 13 C or 14 C; - N represents a nitrogen atom ( 14 N), an isotope 15 N; - 0 represents an oxygen atom ( 16 O), an isotope 17 O or 18 O; - F represents a fluorine atom ( 19 F), an isotope 18 F; - Si represents a silicon atom ( 28 Si), an isotope 29 Si or 30 Si; - S represents a sulphur atom ( 32 S), an isotope 33 S, 34 S or 36 S; - E represents a group R 5 R 6 N- or R 7 O- where - R 5, R 6 and R 7 represent, independently from one another, a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocycle, a group (- -), a silylated group, a siloxy group, an amino group, said alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocycle, silylated, siloxy and amino groups being optionally substituted, or - R 5 and R 6, taken together with the nitrogen atom to which they are bound form an optionally substituted heterocycle, or - R 1 and R 5, taken together with the two nitrogen atoms to which they are respectively bound form an optionally substituted heterocycle, or - R 1 and R 7, taken together with the nitrogen atom and the oxygen atom to which they are respectively bound form an optionally substituted heterocycle, - R 5, R 6 and R 7 optionally comprise an H, C, N, O, F, Si and/or S as defined above, - where R 1, N and O are as defined above; characterised in that an amine of formula is reacted: wherein R 1 and N are as defined above; with CO 2 wherein C and O are as defined above; and in the presence of a catalyst, a silane compound of formula: wherein - H is as defined above, - R 2, R 3 and R 4 represent, independently from one another, a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a silylated group, a siloxy group, an aryl group, an amino group, said alkyl, alkenyl, alkynyl, alkoxy, silylated, siloxy, aryl and amino groups being optionally substituted, or - R 4 is as defined above and R 2 and R 3, taken together with the silicon atom to which they are bound form an optionally substituted silylated, heterocycle, and a nucleophilic agent of formula: E-H wherein E is as defined above and H is a hydrogen atom. - R 1 represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocycle, a carbonyl group (-CO-), a silylated group, a siloxy group, an amino group, said alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocycle, silylated, siloxy and amino groups being optionally substituted, - R 1 optionally comprises an H, C, N, O, F, Si and/or S as defined below; - H represents a hydrogen atom ( 1 H), deuterium ( 2 H) or tritium ( 3 H); - C represents a carbon atom ( 12 C), an isotope 11 C, 13 C or 14 C; - N represents a nitrogen atom ( 14 N), an isotope 15 N; - 0 represents an oxygen atom ( 16 O), an isotope 17 O or 18 O; - F represents a fluorine atom ( 19 F), an isotope 18 F; - Si represents a silicon atom ( 28 Si), an isotope 29 Si or 30 Si; - S represents a sulphur atom ( 32 S), an isotope 33 S, 34 S or 36 S; - E represents a group R 5 R 6 N- or R 7 O- where - R 5, R 6 and R 7 represent, independently from one another, a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a heterocycle, a group (- -), a silylated group, a siloxy group, an amino group, said alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocycle, silylated, siloxy and amino groups being optionally substituted, or - R 5 and R 6, taken together with the nitrogen atom to which they are bound form an optionally substituted heterocycle, or - R 1 and R 5, taken together with the two nitrogen atoms to which they are respectively bound form an optionally substituted heterocycle, or - R 1 and R 7, taken together with the nitrogen atom and the oxygen atom to which they are respectively bound form an optionally substituted heterocycle, - R 5, R 6 and R 7 optionally comprise an H, C, N, O, F, Si and/or S as defined above, - where R 1, N and O are as defined above; - H is as defined above, - R 2, R 3 and R 4 represent, independently from one another, a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, a silylated group, a siloxy group, an aryl group, an amino group, said alkyl, alkenyl, alkynyl, alkoxy, silylated, siloxy, aryl and amino groups being optionally substituted, or - R 4 is as defined above and R 2 and R 3, taken together with the silicon atom to which they are bound form an optionally substituted silylated, heterocycle, and