Enantioselective N‑Heterocyclic Carbene Catalyzed Synthesis of Functionalized Indenes

An enantioselective NHC (N-heterocyclic carbene) catalyzed synthesis of indenes from bifunctional α,β-unsaturated acyl fluorides and TMS enol ethers has been discovered. The reaction has broad generality (31 examples) and proceeds with high levels of enantioselectivity (most >92:8 er). Mechanistically the reaction likely occurs via a Michael/β-lactonization/decarboxylation sequence. Derivatization studies and limitations are discussed

Porous Metal–Organic Framework Catalyzing the Three-Component Coupling of Sulfonyl Azide, Alkyne, and Amine

The robustly porous metal–organic framework MOF–Cu₂I₂(BTTP4) (BTTP4 = benzene-1,3,5-triyl triiso­nicotinate) was shown to work as an efficiently heterogeneous catalyst for the three-component coupling of sulfonyl azides, alkynes, and amines, leading to the formation of <i>N</i>-sulfonyl amidines in good yields. MOF–Cu₂I₂(BTTP4) can be recycled by simple filtration and reused at least four times without any loss in yield. Studies of the ligand effects on the three-component coupling reactions showed that BTTP4 could enhance the rate, as well as the chemoselectivity, when aromatic alkynes were employed. The catalytic process has been thoroughly studied by means of single-crystal and powder X-ray diffraction, gas and solvent adsorption, in situ ¹H NMR and FT-IR spectroscopy, X-ray photoelectron spectra (XPS), and ICP analysis of Cu leaching

Porous Metal–Organic Framework Catalyzing the Three-Component Coupling of Sulfonyl Azide, Alkyne, and Amine

The robustly porous metal–organic framework MOF–Cu₂I₂(BTTP4) (BTTP4 = benzene-1,3,5-triyl triiso­nicotinate) was shown to work as an efficiently heterogeneous catalyst for the three-component coupling of sulfonyl azides, alkynes, and amines, leading to the formation of <i>N</i>-sulfonyl amidines in good yields. MOF–Cu₂I₂(BTTP4) can be recycled by simple filtration and reused at least four times without any loss in yield. Studies of the ligand effects on the three-component coupling reactions showed that BTTP4 could enhance the rate, as well as the chemoselectivity, when aromatic alkynes were employed. The catalytic process has been thoroughly studied by means of single-crystal and powder X-ray diffraction, gas and solvent adsorption, in situ ¹H NMR and FT-IR spectroscopy, X-ray photoelectron spectra (XPS), and ICP analysis of Cu leaching

Enantioselective N‑Heterocyclic Carbene Catalyzed Diene Regenerative (4 + 2) Annulation

An enantioselective N-heterocyclic carbene (NHC)-catalyzed diene regenerative (4 + 2) annulation has been achieved through the use of highly nucleophilic morpholinone-derived catalysts. The reaction proceeds with good to excellent yields, high enantioselectivity (most >92% ee), and good diastereoselectivity (most >7:1). The generality of the reaction is high, with 19 examples reported. The utility of the products has been examined with subsequent derivatization in Diels–Alder reactions using electron-poor dienophiles. Furthermore, interception of the proposed β-lactone intermediate has been achieved, allowing the synthesis of compounds bearing four contiguous stereocenters with high levels of enantio- and diastereoselectivity