Charles E. Loader

Pyrrole chemistry XXV: A simplified synthesis of some 3-substituted pyrroles

Abstract A new synthesis is reported which allows the rapid preparation in good yield of 3-aroyl-, 3-acetyl- and 3-nitro- pyrroles from pyrrole utilizing the 1-benzenesulfonyl group as a blocking group.

Pyrrole chemistry. XXI. Synthetic approaches to cyanopyrroles

The Vilsmeier–Haack reaction with pyrrole and 1-methylpyrrole has been modified to provide a direct synthesis of the corresponding 2-nitriles. Chlorosulfonyl isocyanate may be used to prepare the same compounds, but less satisfactorily. The latter reagent does enable the synthesis of pyrrole-2,4-dicarbonitrile in one step. This dinitrile may be reduced to pyrrole-2,4-dicarboxaldehyde.

Pyrrole chemistry. XXIV. The Vilsmeier formylation and the cyanation of pyrrole acetals. A synthesis of pyrrole-2,3,5-tricarboxaldehyde

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.

Pyrrole Chemistry. Part XXIX A Re-Examination of the Decarboxylation of 4-Acetyl-, 4-Formyl- and 4-Cyanopyrrole-2-Carboxylic Acids

Abstract Decarboxylation of the readily available 4-acyl-2-pyrrolecarboxylic acids has been neglected owing to the poor yields reported in the literature. This study shows that high yields are possible under the correct reaction conditions.