UMWANDLUNG VON 1,3-DIOXANEN ZU 4-OXAALDEHYDEN.

摘要

Prodn. of 4-oxa-aldehydes of formula (R1)-CH-(R2)-O -(R3)-CH-(R4)-C-(R5)-C-O-H (I) comprises isomerisation of 1,3-dioxan cpds. (II) over a catalyst of (1) metal oxide which has been treated with acid and/or (2) SiO2 phases having a zeolite structure. R1,R2,R4, and R5 = H; opt. branched 1-18C alkyl, alkenyl or alkynyl; 5-8C cycloalkyl or cycloalkenyl; 6-16C aryl, alkaryl, aralkyl, aralkenyl or alkenylaryl, or heterocyclyl; or R1 plus R2 and/or R4 plus R5 together complete a cycloalkane, cycloalkene or heterocyclic ring, and all gps. can carry substits. which are inert under the reaction conditions; R3 = H or opt. branched alkyl. The cpds. of formula (I) is new.. (II) are acetals and ketals of 1,3-propanediol (opt. 2-Me, 2,2-Me2; 2,Me-2-Et; 2-Me-2-propyl; 2-Me-2-butyl; 2-Me-2-Ph; or 1-isopropyl-2,2-Me2 substd.) or of 1,1-dimethylol-cyclo(hexane or pentane). Catalysts are oxides of Si, Al, Ti, Zr or Ce, treated with HF, HCl, H3PO4, H3BO3 and/or organic acids. In one pref. procedure SiO2 is refluxed for 1-3hrs., with 0.05-0.5N HF, washed, dried at 100-160 deg.C and calcined at 450-6O0 deg.C. Alternatively, hydrothermally-prepd. phases having the pentasil structure as used, opt. doped with metals such as Cu, Ni, Ce, La or Cs. Reaction is esp. in gas phase at 200-500 (pref. 230-400)deg.C with WHSV 0.1-20 (pref. 0.5-5)g (II)/g catalyst/hr.