Synthesis and transformations of some 1,2,4-trisubstituted pyrroles

Alkyl 1-(2-alkoxy-2-oxoethyl)-4-formyl-1H-pyrrole-2-carboxylates 3a and 3b (alkyl = Me, Et), prepared from the corresponding alkyl 4-formyl-1H-pyrrole-2-carboxylates 2a and 2b, have been modified to other derivatives of the same structural pattern. A series of β-pyrrolylalkenes 4–8 was obtained from pyrrole 3b and various C–acids. Derivatives 2 and 3 have been also used as synthons for polysubstituted 4-(1H-pyrrol-3-yl)-1,4-dihydropyridines 9–12 under the conditions of the standard and the modified Hantzsch’s dihydropyridine synthesis or by regioselective alkylation of the 1,4-dihydropyridine skeleton.