Patent ID: 8212081

Claim:
A process for preparing a substituted 1,4-quinone methide of formula (I) wherein R 1 and R 2 are each independently hydrogen, optionally substituted (C 1 -C 15 )-alkyl, (C 3 -C 15 )-cycloalkyl or (C 6 -C 14 )-aryl, R 7 is optionally substituted (C 1 -C 15 )-alkyl, (C 3 -C 15 )-cycloalkyl or (C 6 -C 14 )-aryl, and X is O or S, comprising: reacting a 3,5-disubstituted 4-hydroxybenzaldehyde of formula (II) wherein R 1 and R 2 are each as defined above, with an orthoformate of formula (III) wherein R 4 , R 5 and R 6 are each independently optionally substituted (C 1 -C 15 )-alkyl, (C 3 -C 15 )-cycloalkyl or (C 6 -C 14 )-aryl, and an alcohol and/or thioalcohol ((thio)alcohol) of formula (IV) wherein R 3 is an optionally substituted (C 1 -C 15 )-alkyl, (C 3 -C 15 )-cycloalkyl or (C 6 -C 14 )-aryl, and X is O or S, in the presence of a at least one catalyst selected from the group consisting of a free or solid-phase-bound organic sulphonic acid, sulphuric acid, a hydrogensulphate, an organic or inorganic phosphorus acid, a dihydrogen or hydrogen salt of an organic or inorganic phosphorous acid, fuming nitric acid and boric acid, to obtain a (thio)acetal; and eliminating the alcohol or thiol from the obtained (thio)acetal to yield the substituted 1,4-quinone methide of formula (I).