The reaction of RhII–oxocarbenoids derived from acyclic diazocarbonyl compounds with phthalimide and succinimide proceeds chemoselectively at the oxygen atom of the imidic carbonyl group, giving rise to the intermediate formation of carbonyl ylides. Intramolecular stabilization of these highly reactive species occurs in three different ways, and is controlled by the structure of the 2-oxocarbenoids. Carbonyl ylides from diazo esters mainly experience a [1,4]-hydrogen shift, and in this case, the corresponding O-alkylimidates are formed as the final products. These ylides may also be stabilized by 1,3-dipolar electrocyclization with intermediate formation of an oxirane. Carbonyl ylides with an acyl group in the carbene moiety undergo an intramolecular 1,5-dipolar electrocyclization to produce 1,3-dioxole derivatives.