We describe that N-nosyl-O-bromoethyl hydroxylamine, a bench stable solid, could function as a novel formaldehyde, formaldimine, and 1,2-oxazetidine surrogate under DBU basic conditions. By merely using this simple reagent, a broad range of synthetically useful α-hydroxymethyl and α-aminomethyl ketones, as well as chiral α-alkoxyl and α-aminomethyl indanone carboxylates could be divergently obtained via chemo- and stereoselective aldol, Mannich or umpolung C–O bond-forming reactions. The challenging catalytic asymmetric Mannich reaction of formaldimine equivalent was also realized with moderate enantioselectivities.