7476-66-6Relevant articles and documents
A π–Cu(II)?π Complex as an Extremely Active Catalyst for Enantioselective α-Halogenation of N-Acyl-3,5-dimethylpyrazoles
Nishimura, Kazuki,Wang, Yanzhao,Ogura, Yoshihiro,Kumagai, Jun,Ishihara, Kazuaki
, p. 1012 - 1017 (2022/01/19)
Novel chiral π–copper(II)?π complex catalyzed enantioselective α-chlorination and -bromination of N-acyl-3,5-dimethylpyrazoles are described. The π–copper(II)?π complexation of Cu(OTf)2 with 3-(2-naphthyl)-l-alanine-derived amides greatly increases the Lewis acidity and triggers the in situ generation of enolate species without an external base, which has a suppressing effect for α-chlorination and -bromination due to undesired halogen bonding. This strategy provides facile access to α-halogenated compounds in high yield with excellent enantioselectivity. X-ray crystallographic and ESR analyses of the catalyst complexes suggest that the release of two counteranions (2TfO–) from the copper(II) center might be crucial for the efficient activation of N-acyl-3,5-dimethylpyrazoles.
Visible Light-Promoted Sulfoxonium Ylides Synthesis from Aryl Diazoacetates and Sulfoxides
Lu, Juan,Li, Lei,He, Xiang-Kui,Xu, Guo-Yong,Xuan, Jun
, p. 1646 - 1650 (2021/05/28)
A visible light-promoted reaction of donor/acceptor diazoalkanes with sulfoxides towards the synthesis of synthetically useful sulfoxonium ylides was reported. The reaction occurred under sole visible light irradiation without the need of any transition-metals or additives, affording the corresponding sulfoxonium ylides in moderate to good yields. The success of late-stage modification of natural isolates or drug candidates, scale-up reaction and transformation of sulfoxonium ylides to other useful molecules further rendered the approach valuable.
Straightforward Access to Terminally Disubstituted Electron-Deficient Alkylidene Cyclopent-2-en-4-ones through Olefination with α-Carbonyl and α-Cyano Secondary Alkyl Sulfones
Afri, Michal,Gruzman, Arie,Korshin, Edward E.,Leitus, Gregory,Palczewski, Krzysztof,Rothstein, Ayelet,Trifonov, Lena,Viskind, Olga
supporting information, p. 6725 - 6736 (2021/12/31)
Herein we report on a simplified synthesis of scarcely explored, terminally disubstituted electron-poor alkylidene cyclopent-2-en-4-ones through uncommon olefination. Secondary sulfones, activated by electron-withdrawing groups at the adjacent carbon atom, undergo K2CO3-promoted coupling with 4-acyloxy- and 4-tert-butyldimethylsilyloxycyclopent-2-en-1-ones giving directly, or after a separate dehydrosulfinylation step, alkylidene cyclopent-2-en-4-ones. A plausible mechanism for these transformations is proposed. Initially, β-arylsulfonyl esters as well as their acetyl or nitrile analogues are allylated by cyclopentenone derivatives via a tandem Michael addition of α-sulfonyl carbanions followed by proton migration and retro-Michael-type O-nucleofuge elimination. The primary allylation products are formed as two diastereomers whose configuration and conformation were elucidated using single crystal X-ray diffraction and NMR spectroscopy. Regardless of stereochemistry, both sets of diastereomers are subjected to Zaitsev-type retro-Michael vinylogous dehydrosulfinylation under either basic or thermal silica gel promoted conditions resulting in E/Z-alkylidene cyclopent-2-en-4-ones. In these reactions activated sulfones serve as bearing electron-withdrawing group alkylidene anion-radical synthons, whereas 4-oxy-substituted cyclopentenones represent cyclopent-2-en-4-one cation-radical surrogates.
