Medium ring lactones and lactams are widespread subunits inbiologically active natural products and therapeutic agents.The development of efficient strategies for their assembly has been a longstanding topic in organic synthesis.Although significant progress has been achieved in the past few decades, new strategies are in high demand.Enabled by the design of new amphoteric molecules as well as new ring expansion strategies, we have developed several intermolecular reactions that not only efficiently assemble these challenging medium ring systems, but also oroceed under mild conditions without high dilution or slow addition.