Intramolecular C–H insertion reactions of a-diazocarbonyl compounds typically proceed with preferential five-membered ring formation. However, the presence of a heteroatom such as nitrogen can activate an adjacent C–H site toward insertion resulting in regiocontrol issues. In the case of a-diazoacetamide derivatives, both ß- and ¿-lactam products are possible owing to this activating effect. Both ß- and ¿-lactam products are powerful synthetic building blocks in the area of organic synthesis, as well as a common scaffold in a range of natural and pharmaceutical products and therefore C–H insertion reactions to form such compounds are attractive processes.Intramolecular C–H insertion reactions of a-diazocarbonyl compounds typically proceed with preferential five-membered ring formation. However, the presence of a heteroatom such as nitrogen can activate an adjacent C–H site toward insertion resulting in regiocontrol issues. In the case of a-diazoacetamide derivatives, both ß- and ¿-lactam products are possible owing to this activating effect. Both ß- and ¿-lactam products are powerful synthetic building blocks in the area of organic synthesis, as well as a common scaffold in a range of natural and pharmaceutical products and therefore C–H insertion reactions to form such compounds are attractive processes.