Ortho-Nitro Effect on the Diastereoselective Control in Sulfa-Staudinger and Staudinger Cycloadditions

Yang, Zhanhui; Abdellaoui, Hassane; He, Wei; Xu, Jiaxi

doi:10.3390/molecules22050784

Cited by 4 publications

References 47 publications

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Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Zhang,

Liu,

Wang

et al. 2024

ChemistrySelect

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The annulation of arynes with dibenzo[b,f][1,4]oxazepines (N‐aryl cyclic imines) in the presence of CO2 has been studied in comparison with 3,4‐dihydroisoquinolines (N‐alkyl cyclic imines). For the reaction with dibenzo[b,f][1,4]oxazepines, [2+2] annulation takes place specifically with arynes, with CO2 acting only as the protecting gas. 3,4‐dihydroisoquinolines, however, exclusively underwent [2+2+2] annulation with arynes and CO2, with CO2 as a reactant. Our findings offer insights into imine‐aryne annulation under CO2 and suggest that steric and nucleophilic factors control the annuloselectivity. Reactivity analysis revealed that electron‐rich and less steric N‐alkyl cyclic imines and electron‐deficient benzynes favor the [2+2+2] annulation, while electron‐deficient and bulky N‐aryl cyclic imines prefer the [2+2] annulation. In the [2+2] annulation, the Hammett analyses reveal that both the nucleophilic attack of imines to benzynes (the first step, negative ρ) and the attack of phenyl anions on the iminium species (the second step, positive ρ) affect the reaction rate.

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Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Zhang,

Liu,

Wang

et al. 2024

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Sterically controlled diastereoselectivity in thio-Staudinger cycloadditions of alkyl/alkenyl/aryl-substituted thioketenes

Zhuang

Yang

et al. 2017

Org. Biomol. Chem.

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The [2 + 2] cycloadditions of thioketenes and imines are named as thio-Staudinger cycloadditions. The diastereoselectivity in thio-Staudinger cycloaddtions of alkyl/alkenyl/aryl-substituted thioketenes is rationalized. The steric effects of the thioketenes play an extremely important role in deciding the diastereoselectivity (cis/trans selectivity) through controlling exo- and endo-attack and subsequent ring closure. The conclusion is further supported by our additional experimental and calculational results. The isomerization of the iminium moiety in zwitterionic intermediates generated from the thioketenes and linear imines also affects the diastereoselectivity. The electronic effect of imine substituents slightly impacts the diastereoselectivity, while epimerization of cis-β-thiolactams to trans-diastereomers is a significant factor in the thio-Staudinger cycloadditions of mono-substituted thioketenes under basic conditions.

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Stereochemistry and mechanistic insights in the [2^t + 2ⁱ + 2ⁱ] annulations of thioketenes and imines

Zhuang

et al. 2017

Org. Biomol. Chem.

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Stereochemical models and mechanistic insights are proposed for [2 + 2 + 2] annulations of thioketenes and imines on the basis of experimental and computational investigations. In the [2 + 2 + 2] annulations involving cyclic imines, the zwitterionic intermediates generated from monosubstituted thioketenes and the cyclic imines undergo a stepwise nucleophilic endo-addition/Si-face attack pathway with a second imines molecule, giving initially (2,4)-cis-(4,5)-cis-[2 + 2 + 2] annuladducts, which completely epimerize into the corresponding (2,4)-cis-(4,5)-trans-annuladducts under basic reaction conditions. The annuloselectivity of thio-Staudinger cycloadditions is dependent on the substituents of both thioketenes and imines. The reactivities and annuloselectivities of Staudinger, thio-Staudinger, and sulfa-Staudinger intermediates are compared.

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Ortho-Nitro Effect on the Diastereoselective Control in Sulfa-Staudinger and Staudinger Cycloadditions

Cited by 4 publications

References 47 publications

Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Sterically controlled diastereoselectivity in thio-Staudinger cycloadditions of alkyl/alkenyl/aryl-substituted thioketenes

Stereochemistry and mechanistic insights in the [2^t + 2ⁱ + 2ⁱ] annulations of thioketenes and imines

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Ortho-Nitro Effect on the Diastereoselective Control in Sulfa-Staudinger and Staudinger Cycloadditions

Cited by 4 publications

References 47 publications

Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO2: [2+2] vs [2+2+2] Annulation

Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO2: [2+2] vs [2+2+2] Annulation

Sterically controlled diastereoselectivity in thio-Staudinger cycloadditions of alkyl/alkenyl/aryl-substituted thioketenes

Stereochemistry and mechanistic insights in the [2t + 2i + 2i] annulations of thioketenes and imines

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Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Annuloselectivity of Dibenzoxazepines and Arynes in the Presence of CO₂: [2+2] vs [2+2+2] Annulation

Stereochemistry and mechanistic insights in the [2^t + 2ⁱ + 2ⁱ] annulations of thioketenes and imines