Cu(I)-Catalyzed Oxidative Cyclization of Alkynyl Oxiranes and Oxetanes

Abstract

In the presence of a Cu(I) catalyst and a pyridine oxide, alkynyl oxiranes and oxetanes can be converted into functionalized five- or six-membered α,β-unsaturated lactones or dihydrofuranaldehydes. This new oxidative cyclization is proposed to proceed via an unusual allenyloxypyridinium intermediate.

Recent Applications of Oxetanes in the Synthesis of Heterocyclic Compounds

“…12 An interesting divergence in product selectivity was delivered by varying the nature of the pyridine oxide oxidant.…”

Ring Expansions of Oxiranes and Oxetanes

“…Professor Gagosz recently reported an innovative catalytic conversion of alkynyl oxiranes to butenolides (Scheme 24) [36]. A Cu(I) catalyst is used to activate the alkynyl oxiranes, which then react with pyridine-oxide to form an α-alkoxy allene.…”

“…Professor Gagosz also evaluated oxetane substrates (Scheme 41) as candidates for this copper-catalyzed alkynyl oxirane ring-expansion reaction (Scheme 24) [36]. Most interestingly, and different from the oxirane substrates, was the dependence on the type of pyridine N-oxides employed.…”

An Alternative Reaction Outcome in the Gold‐Catalyzed Rearrangement of 1‐Alkynyloxiranes

“…[2] Considering the ability of gold catalysts to activate alkynes, [3] Hashmi et al elegantly developed a mild and functional group compatible protocol to achieve this interesting transformation making use of AuCl 3 as catalyst (Scheme 1a). [9] Considering the strong influence of the structure of the substrates in gold-catalyzed transformations, [3] we envisioned that the replacement of H atoms in the oxirane ring by different substituents might translate into a different reactivity (Scheme 1c). [8] Notably, these studies have been exclusively focused on di-and trisubstituted oxiranes, whereas the use of the corresponding tetrasubstituted analogues remained unexplored.…”