Reactions between pyrrole and orthoesters: preparation of tri-(pyrrol-2-yl)alkanes

Reactions between triethyl orthoformate, trimethyl orthoacetate and triethyl orthopropionate with pyrrole and chloroacetic acid lead to moderate yields of the corresponding tri-(pyrrol-2-yl)alkanes 5a, 5b and 5c, respectively. Under the same conditions, trimethyl orthobenzoate reacts with pyrrole and dichloroacetic acid to give the dipyrrin 7 in a relatively good yield.