Process for preparing alkylidene-substituted-1, 4-dions derivatives

A process for preparing 2,3-disubstituted-alkylidene-1,4 dions derivatives of formula (IVa), (IVb) or (IVc) or a mixture thereof:

• wherein R1 and R2, equal to or different from each other, are hydrogen atoms or C1-C20 hydrocarbon groups, optionally containing heteroatoms belonging to group 13-17 of the periodic table, or R1 and R2 can join together to form a saturated or unsaturated C3-C10 ring, optionally containing heteroatoms belonging to group 13-17 of the periodic table, with the proviso that when R1 and R2 are both hydrogen atoms, only compounds of formula (IVa) or (IVb) are obtained;
• T2 is H, OR4, R4, NR42, SR4 or PR42;
• R4, equal to or different from each other, are a C1-C20 hydrocarbon group, optionally containing one or more heteroatoms belonging to group 13-17 of the periodic table;
• R5 and R6, equal to or different from each other, are hydrogen atoms or C1-C20 hydrocarbon groups, optionally containing heteroatoms belonging to group 13-17 of the periodic table, or R5 and R6 can join together to form a saturated or unsaturated C3-C10 ring, optionally containing heteroatoms belonging to group 13-17 of the periodic table;
• with the proviso that R5 and R6 are not hydrogen at the same time;
• said process comprising the following steps:
• a) reacting a compound of formula (II)
• with a compound of formula (Va) or (Vb)
• in the presence of at least one equivalent with respect to the compound of formula (Va) or (Vb) of a salt of a base or a neutral base at a temperature higher than 70° C.;
• b) treating the compound obtained in step a) with a compound of formula (VI):
• in the presence of a reaction medium and a base;
• and
• c) esterifying the product obtained in step b).