Improved synthesis of an expoxidation-catalyst

Process to produce compounds of formula (I)

• wherein in a first step (step (i) the compound of formula (II),
• is reacted with a compound of formula (IV)
• wherein
• R1 is H or a C1-C3 alkyl group (preferably —H, —CH3 or —CH2CH3), and
• R2 is a C1-C3 alkyl group (preferably —CH3 or —CH2CH3), and
• R3 is H or a C1-C2 alkyl group (preferably —H or —CH3),
• wherein R is a C1-C3 alkyl group in the presence of a solid acid catalyst and wherein the reaction product of step (ii), which is the compound of formula (III)
• wherein
• R1 is the same as defined for the compound of formula (IV),
• is oxidized to a compound of formula (I).