Verfahren zur Herstellung von Enolethern

摘要

The preparation of enol-ethers of formula R3R4C=C(OR1)R2 is by gas phase reaction at 100-550 (especially 200-350) degrees C and 0.001-5 bar of acetals or ketals of formula R3R4HC-C(OR1)(OR1')R2 on a heterogeneous highly porous catalyst which is an oxide of a Gp. II, III or IV or sub-Gp. II or IV element, the catalyst having a pH of 7-14, a porosity of 40-80% and a BET surface area of 0.5-250 m<2>/g. R1-5 = 1-20 C alkyl, 2-20 C alkenyl or 7-20 C phenylalkyl; R2-4 = H, aryl, CN, COOR5, 1-12 C alkyl (optionally 1-3 times substituted or interrupted by COOR5, CO, CN or 1-12 C alkoxy), aryl or 7-12 C phenylalkyl (each optionally 1-3 times substituted by 1-12 C alkyl, 1-12 C alkoxy, halogen or CN); R2/R4 or R3/R4 = together 3-10 C alkylene or 2-20 C alkylidene; and R1' = R1, but not necessarily the same.