A ruthenium porphyrin-catalyzed stereoselective intramolecular carbenoid CH insertion is described. Using [RuII (TTP)(CO)] as catalyst, aryl tosylhydrazones are converted to 2, 3- dihydrobenzofurans, 2, 3-dihydroindoles, and β-lactams in good yields and remarkable cis selectivity (up to 99%). Enantioselective synthesis of 2, 3-dihydrobenzofurans is also achieved with [RuII (D4-Por*)(CO)] as catalyst, and up to 96% ee is attained.