Pyrrole　formiate　derivatives　were　synthesized　through　ring　contraction　of　corresponding　3-carboxylate-1,4-dihydropyridines　(3-CDHPs)　mediated　by　2,2,6,6-tetramethylpiperidine-N-oxyl　(TEMPO).　2-Carboxylate-3-aryl-1H-pyrroles　(2)　and　3-carboxylate-4-aryl-IH-pyrroles　(3)　were　obtained　under　readily　accessible　reaction　conditions.　To　gain　deep　insights　into　this　transformation,　DFT　calculations　were　carried　out　to　establish　the　plausible　reaction　mechanism.　The　result　revealed　that　the　processes,　including　release　of　hydrogen,　coupling　with　TEMPO,　ring-opening　of　DHP　scaffold,　cleavage　of　O-N　bond　in　TEMPO　moiety,　fabrication　of　pyrrole　scaffold　and　dissociation　of　formyl　were　incorporated　in　the　transformation,　which　was　confirmed　further　by　the　characterization　of　a　byproduct　and　the　detection　of　key　intermediates　using　the　LC-MS　method.　(C)　2018　Elsevier　Ltd.　All　rights　reserved.