1: pyrrole-3-carboxylic acid ethyl ester With sodium hydride in N,N-dimethyl-formamide; mineral oil T=0°C; 2: benzyl bromide in N,N-dimethyl-formamide; mineral oil T=0 - 20°C;

manganese(IV) oxide in tetrahydrofuran Heating;

N-bromosuccinmide T=90°C; 19 h; or with DDQ in refluxing toluene, or with p-chloranil, or with O2 in dioxane at 90 deg C; other N-protected 2,5-dihydro-1H-pyrroles; Product distribution;