132927-05-0Relevant articles and documents
Stereocontrolled Synthesis of Sulfonyl 2,5-Diaryltetrahydrofurans
Chang,Cheng
, p. 854 - 858 (2016)
BF3·OEt2-mediated stereocontrolled annulation of 4-alkenols affords sulfonyl 2,5-diaryltetrahydrofurans in good yields. The key synthetic route combines the facile stereoselective reduction of α-styryl-β-ketosulfones and an intramole
Role of Electron-Deficient Olefin Ligands in a Ni-Catalyzed Aziridine Cross-Coupling to Generate Quaternary Carbons
Estrada, Jesús G.,Williams, Wendy L.,Ting, Stephen I.,Doyle, Abigail G.
, p. 8928 - 8937 (2020)
We previously reported the development of an electron-deficient olefin (EDO) ligand, Fro-DO, that promotes the generation of quaternary carbon centers via Ni-catalyzed Csp3-Csp3 cross-coupling with aziridines. By contrast, electronically and structurally similar EDO ligands such as dimethyl fumarate and electron-deficient styrenes afford primarily β-hydride elimination side reactivity. Only a few catalyst systems have been identified that promote the formation of quaternary carbons via Ni-catalyzed Csp3-Csp3 cross-coupling. Although Fro-DO represents a promising ligand in this regard, the basis for its superior performance is not well understood. Here we describe a detailed mechanistic study of the aziridine cross-coupling reaction and the role of EDO ligands in facilitating Csp3-Csp3 bond formation. This analysis reveals that cross-coupling proceeds by a Ni0/II cycle with a NiII azametallacyclobutane catalyst resting state. Turnover-limiting C-C reductive elimination occurs from a spectroscopically observable NiII-dialkyl intermediate bound to the EDO. Computational analysis shows that Fro-DO accelerates turnover limiting reductive elimination via LUMO lowering. However, it is no more effective than dimethyl fumarate at reducing the barrier to Csp3-Csp3 reductive elimination. Instead, Fro-DO's unique reactivity arises from its ability to associate favorably to NiII intermediates. Natural bond order second-order perturbation theory analysis of the catalytically relevant NiII intermediate indicates that Fro-DO binds to NiII through an additional stabilizing donor-acceptor interaction between its sulfonyl group and NiII. Design of new ligands to evaluate this proposal supports this model and has led to the development of a new and tunable ligand framework.
Visible-light-promoted radical alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester: Synthesis of oxazolines
Ding, Hao,Huang, Panyi,Jin, Can,Su, Weike,Sun, Bin,Yan, Zhiyang,Zhao, Haiyun
, (2021/10/29)
An efficient photocatalytic alkylation/cyclization of allylic amide with N-hydroxyphthalimide ester has been developed. The transformation is taken advantage of alkyl radicals to attack allylic amide with the assist of inexpensive rose bengal as photocatalyst to prepare a series of alkyl substituted oxazolines in moderate to excellent yields. High regioselectivity, operational safety, mild conditions and excellent substrate generality give this protocol broad application prospects.
Asymmetric [2+2] photocycloadditionviacharge transfer complex for the synthesis of tricyclic chiral ethers
Martínez-Gualda, Ana M.,Domingo-Legarda, Pablo,Rigotti, Thomas,Díaz-Tendero, Sergio,Fraile, Alberto,Alemán, José
supporting information, p. 3046 - 3049 (2021/03/29)
The asymmetric synthesis of chiral polycyclic ethers by an intramolecular [2+2] photocycloaddition is described. This process proceeded through a photocatalytically active iminium ion-based charge transfer (CT) complex under visible light irradiation. In this way a stereocontrolled [2+2] photocycloaddition is enabled leading to tricyclic products with good enantiomeric ratios.
