s-Tetrazine: robust and green photo-organocatalyst for aerobic oxidation of N,N-disubstituted-hydroxylamines to nitrones

Efficient photocatalytic aerobic oxidative dehydrogenation reaction of N,N-disubstituted hydroxylamines to nitrones were developed with an in situ generated photocatalyst based on commercially available 3,6-dichlorotetrazine. This process affords a wide range of nitrones in high yields under mild conditions. In addition, an oxidative (3+3) cycloaddition between an oxyallyl cation precursor and a hydroxylamine was also developed.

Oxyallyl Cation Promoted Dearomative Semipinacol Rearrangement: Facile Stereodivergent Synthesis of Spiro-indolines with Contiguous Quaternary Centers

A novel oxyallyl cation promoted semipinacol rearrangement of indole-type allylic alcohols was disclosed for the stereo-divergent synthesis of spiro-indolines. A variety of spiro-indolines were obtained with moderate to good yields....

Transition metal-free synthesis of α-aryl ketones via oxyallyl cation capture with arylboronic acids

α-Arylated ketones were accessed via oxyallyl cation capture with arylboronic acids in good yields with broad substrate tolerance.

Catalytic palladium-oxyallyl cycloaddition

Exploration of intermediates that enable chemoselective cycloaddition reactions and expeditious construction of fused- or bridged-ring systems is a continuous challenge for organic synthesis. As an intermediate of interest, the oxyallyl cation has been harnessed to synthesize architectures containing seven-membered rings via (4+3) cycloaddition. However, its potential to access five-membered skeletons is underdeveloped, largely due to the thermally forbidden (3+2) pathway. Here, the combination of a tailored precursor and a Pd(0) catalyst generates a Pd-oxyallyl intermediate that cyclizes with conjugated dienes to produce a diverse array of tetrahydrofuran skeletons. The cycloaddition overrides conventional (4+3) selectivity by proceeding through a stepwise pathway involving a Pd-allyl transfer and ring closure sequence. Subsequent treatment of the (3+2) adducts with a palladium catalyst converts the heterocycles to the carbocyclic cyclopentanones.

Highly efficient [3+3] cycloaddition reactions of in situ generated aza-oxyallyl cation with nitrones

An efficient protocol was developed for the synthesis of 1,2,4-oxadiazinan-5-one derivatives via [3+3] cycloaddition ofin situgenerated aza-oxyallyl cations with nitrones. This method provides high yields of the heterocyclic products, excellent regioselectivity and broad substrate scope.