to vinyl ether, the pathways leading to mono‐ and bis‐adducts must compete on the level of the intermediate l,4‐zwitterions 1 and 2. The latter either cyclize to the cyclobutanes 3 or to six‐membered cyclic ketene imines 8 which accept a second molecule of vinyl ether to yield the bis‐adducts 6. The occurrence of the highly strained ketene imines 8 gains credibility by comparison to stable seven‐membered