The preparation of the acetals of a number of pyrrole mono- and dicarboxaldehydes is described. It is shown that, provided the reactivity of the unsubstituted ring positions on the pyrrole nucleus is not too low, a carboxyaldehyde or a carbonitrile group may be substituted onto the pyrrole ring using the Vilsmeier reaction or chlorosulfonyl isocyanate respectively. Vilsmeier formylation of the diacetal, 2,4-di(5,5-dimethyl- 1,3-dioxan-2-yl)-pyrrole, followed by hydrolysis gave pyrrole-2,3,5-tricarboxaldehyde.
描述了一系列
吡咯单酸和二酸的
缩醛制备方法。结果表明,只要
吡咯核上未取代的位置的反应性不太低,可以使用Vilsmeier反应或
氯磺酰异氰酸酯将羧醛或碳
氰基取代到
吡咯环上。对二
缩醛2,4-二(5,
5-二甲基-1,3-二氧杂
环戊烷-2-基)-
吡咯进行Vilsmeier甲酰化反应,然后
水解得到
吡咯-2,3,5-三酸醛。