| abstract |
The invention relates to a process for the preparation of * Here are * of the general formula I with the addition of silyl halides as catalyst at reaction temperatures of 20C to 45C in the * the general formula II converted, these isolated, or these without intermediate isolation at reaction temperatures of 10C to 60C subjected to the acid-catalyzed acetal cleavage at p H 1.6 to 2.4 and the * of the general formula III directly separated from the reaction mixture in crystalline form. In the general formulas I to III, R1 is CH3, C2H5; R2OH, R3H, CH3, CCH or R2, R3O; R4, R5CH3, C2H5, CH2CH2CH3 {production process; * * Silyl halides; Catalyst; * acid-catalyzed; acetal; isomerization} |