Preparation of 1,2-Oxazetidines from Styrenes and Arylamines via a Peroxide-Mediated [2 + 1 + 1] Cycloaddition Reaction

Synthesis of 1,2-oxazetidines with a free -NH group via photoredox catalysis

A photoredox approach enabling one-step synthesis of oxazetidines with a free -NH group via the combined use of alkyne, thiophenol, and azide has been reported. The synthesized oxazetidine with the free -NH group was stable enough for various late-stage transformations such as methylation, acetylation, tosylation, and ring-opening reaction to afford synthetically useful α-aminoketones.

Highly Selective Synthesis of 2-tert-Butoxy-1-Arylethanones via Copper(I)-Catalyzed Oxidation/tert-Butoxylation of Aryl Olefins with TBHP

A practical and environmentally friendly protocol for the selective oxidation of aryl olefins to arylethanone derivatives by using a Cu(I) catalyst and tert-butyl hydroperoxide (TBHP) has been developed. A series of 2-tert-butoxy-1-arylethanones were obtained in moderate to good yields under mild conditions with high selectivity. In this method, TBHP acts not only as an oxidant but also as the tert-butoxy and carbonyl oxygen sources. This enables one-step oxidation/tert-butoxylation. Various allyl peroxides were also synthesized from allyl substrates.

Regio- and chemoselective synthesis of nitrogen-containing heterocycles via the oxidative cascade cyclization of unactivated 1,n-enynes

The development of a method for performing radical initiated intramolecular cascade cyclization of 1,n-enynes provided a competent protocol for producing structurally diverse complex heterocycles.

Intermolecular scandium triflate-promoted nitrene-transfer [5 + 1] cycloadditions of vinylcyclopropanes

Sc(OTf)3-promoted [5 + 1] cycloaddition of vinylcyclopropanes with PhINTs is reported, enabling the regioselective preparation of a range of 1,2,3,6-tetrahydropyridine scaffolds under mild conditions. This represents the second example of a [5 + 1] nitrene-transfer cycloaddition and exhibits complementary substrate scope to the antecedent work, expanding the range of N-heterocycles accessible via this strategy.

Rh(II)-Catalyzed Nitrene-Transfer [5 + 1] Cycloadditions of Aryl-Substituted Vinylcyclopropanes

Formal [5 + 1] cycloadditions between aryl-substituted vinylcyclopropanes and nitrenoid precursors are reported. The method, which employs Rh₂(esp)₂ as a catalyst, leads to the highly regioselective formation of substituted tetrahydropyridines. Preliminary mechanistic studies support a stepwise, polar mechanism enabled by the previously observed Lewis acidity of Rh-nitrenoids. Overall, this work expands the application of nitrene-transfer cycloaddition, a relatively underexplored approach to heterocycle synthesis, to the formation of six-membered rings.