Alkynylation oxiranes and oxetanes

In the presence of catalytic amount of Cu(NCMe)4NTf2 (4 mol %), 4-methoxypyridine A -oxide (2 equiv) promotes the oxidative cyclization of alkynyl oxiranes and oxetanes (eqs 15 and 16). The mild reaction conditions tolerate a breath of functional groups such as distal epoxides, alkynes, ethers, acetamide, tosylamide, and aryl halides. 

Alkynyl oxiranes and oxetanes in the presence of a Cu(I) catalyst and a pyridine oxide give five- or six-membered a,j0-unsaturated lactones or dihydrofuranaldehydes in an oxidative cyclization via an allenyloxypyridinium intermediate (Scheme 100). ... 

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