| 摘要 |
The invention concerns a process for preparing 2-substituted but-2-ene-1,4-dial-acetals of general formula (I) in which the substituents R<1> to R<4> stand for hydrogen or C1-C6 aliphatic groups and R<2> and R<3> or R<1> and R<2> in each case are common members of an aliphatic 4- to 7-member ring which can contain a heteroatom, and in which R<5> designates a C1-C12 alkyl, alkenyl or alkinyl group, which can be substituted by cycloaliphatic, aromatic or heterocyclic groups or by hydroxy, ether, thioether, acyl, alkylamino, carboxy or carbalkoxy groups, an optionally substituted aryl group or an alkoxy, alkylthio or acyloxy group. According to the invention: a) glyoxal is reacted with a 1,3-propane diol of general formula (II) in an aqueous solution in the presence of an acid to form a monoacetal of general formula (III), the reaction solution is neutralized and optionally the volatile components which are lighter than the monoacetal (III) are distilled off; b) the resultant monoacetal (III) is reacted with an aldehyde R<5>-CHO in the presence of between 0.01 and 10 mol %, relative to glyoxal, of a catalyst mixture consisting of a secondary amine and an acid to form an aldol of general formula (IV), and optionally the volatile components which are lighter than the aldol (IV) are distilled off; and c) the aldol (IV) is dehydrogenated in the presence of a dehydrating agent to form product (I). The invention also concerns novel hemiacetals of glyoxalmonoacetals. |
