Catalytic Asymmetric γ-Alkylation of Carbonyl Compounds via Stereoconvergent Suzuki Cross-Couplings
摘要:
With the aid of a chiral nickel catalyst, enantioselective gamma- (and delta-) alkylations of carbonyl compounds can be achieved through the coupling of gamma-haloamides with alkylboranes. In addition to primary alkyl nucleophiles, for the first time for an asymmetric cross-coupling of an unactivated alkyl electrophile, an arylmetal, a boronate ester, and a secondary (cyclopropyl) alkylmetal compound are shown to couple with significant enantioselectivity. A mechanistic study indicates that cleavage of the carbon-halogen bond of the electrophile is irreversible under the conditions for asymmetric carbon-carbon bond formation.
A new radical cyclization method for the formation of C(sp3)–C(sp3) and C–O bonds via MnO2-promoted alkene carboesterification with anhydrides is developed.
Gallium-catalyzed reductive lactonization of γ-keto acids with a hydrosilane
作者:Norio Sakai、Shuhei Horikawa、Yohei Ogiwara
DOI:10.1039/c6ra19286f
日期:——
Described herein is the GaCl3-catalyzed lactonization of γ-keto carboxylic acids in the presence of PhSiH3 leading to the direct preparation of γ-lactone derivatives. This reducing system showed a relatively wide functional group tolerance.
Indium-Catalyzed Direct Conversion of Lactones into Thiolactones and Selenolactones in the Presence of Elemental Sulfur and Selenium
作者:Norio Sakai、Shuhei Horikawa、Yohei Ogiwara
DOI:10.1055/s-0036-1591849
日期:2018.2
Abstract The direct conversion of lactones into thiolactones with elemental sulfur (S8) catalyzed by InCl3/PhSiH3 in a one-pot reaction is described. This catalytic system was successfully applied to the novel preparation of selenolactones from lactones and selenium. The direct conversion of lactones into thiolactones with elemental sulfur (S8) catalyzed by InCl3/PhSiH3 in a one-pot reaction is described
A practical route from oxetane or thietane to γ‐(thio)butyrolactone via solvated‐proton‐assisted cobalt‐catalyzed carbonylative ring expansion under syngas atmosphere has been established. A wide variety of γ‐(thio)butyrolactones can be afforded in good to excellent yields. The versatility of this method has been well demonstrated in the synthesis of intermediates towards the natural product Arctigenin
Photocatalytic Synthesis of γ-Lactones from Alkenes: High-Resolution Mass Spectrometry as a Tool To Study Photoredox Reactions
作者:Ierasia Triandafillidi、Maroula G. Kokotou、Christoforos G. Kokotos
DOI:10.1021/acs.orglett.7b03256
日期:2018.1.5
A mild photocatalytic manifold for the synthesis of γ-lactones has been developed. Utilizing Ru(bpy)3Cl2 as the photocatalyst, a cheap and reproducible synthetic protocol for γ-lactones has been introduced. Mechanistic studies revealed the successful monitoring of photocatalyticreactions and radical intermediates via high-resolution mass spectrometry.