[摘要]：Readily available five- and six-membered lactones and N-sulfonyllactams undergo efficient addn. of t-Bu propiolate, and the resulting adducts undergo cycloisomerization to six- and seven-membered cyclic ethers or amines in the presence of pyridinium acetate. The ring expansion process occurs in generally good yields and is proposed to involve a nucleophilic catalysis mechanism.
