1‑Hydroxybenzotriazole-Assisted, N‑Heterocyclic Carbene Catalyzed β‑Functionalization of Saturated Carboxylic Esters: Access to Spirooxindole Lactones

A 1-hydroxybenzotriazole-assisted, N-heterocyclic carbene catalyzed direct β-functionalization of saturated carboxylic esters is disclosed. This formal [3 + 2] annulation reaction of carboxylic esters with isatins affords optically pure spirooxindole lactones (on gram scale) bearing two vicinal stereogenic centers. A dual role of HOBt is proposed based on controlled experiments to rationalize the enhancement of diastereoselectivity and enantioselectivity

Hydroxyphosphinylation Reaction of 3‑Cyclopropylideneprop-2-en-1-ones via C–P σ‑Bond Cleavage

An unexpected hydroxyphosphinylation of 3-cyclopropylideneprop-2-en-1-ones with phosphines has been observed. This method provides a unique regio- and stereoselective synthesis of highly functionalized 1-dialkylphinyl-3-oxo-(1<i>Z</i>)-alkenyl cyclopropanols with important potentials. The reaction displays an unusual mechanistic featurea highly selective cleavage of C–P σ bonds in phosphines

Hydroxyphosphinylation Reaction of 3‑Cyclopropylideneprop-2-en-1-ones via C–P σ‑Bond Cleavage

An unexpected hydroxyphosphinylation of 3-cyclopropylideneprop-2-en-1-ones with phosphines has been observed. This method provides a unique regio- and stereoselective synthesis of highly functionalized 1-dialkylphinyl-3-oxo-(1<i>Z</i>)-alkenyl cyclopropanols with important potentials. The reaction displays an unusual mechanistic featurea highly selective cleavage of C–P σ bonds in phosphines

Free vibration analysis of composite cylindrical shells with non-uniform thickness walls

The paper proposes to characterize the free vibration behaviour of non-uniform cylindrical shells using spline approximation under first order shear deformation theory. The system of coupled differential equations in terms of displacement and rotational functions are obtained. These functions are approximated by cubic splines. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector which are spline coefficients. Four and two layered cylindrical shells consisting of two different lamination materials and plies comprising of same as well as different materials under two different boundary conditions are analyzed. The effect of length parameter, circumferential node number, material properties, ply orientation, number of lay ups, and coefficients of thickness variations on the frequency parameter is investigated

PdCl₂-Catalyzed Oxidative Cycloisomerization of 3-Cyclopropylideneprop-2-en-1-ones

A novel PdCl₂-catalyzed oxidative cycloisomerization of 3-cyclopropylideneprop-2-en-1-ones, providing a facile synthesis of highly strained functionalized 2-alkylidenecyclobutanones via furan-fused cyclobutene intermediates, is reported. An interesting route to 2(3<i>H</i>)-furanones with a spiro-cyclopropane unit from the obtained 2-alkylidenecyclobutanones via a ring-contraction rearrangement reaction is also realized

I₂‑Catalyzed Oxidative Coupling Reactions of Hydrazones and Amines and the Application in the Synthesis of 1,3,5-Trisubstituted 1,2,4-Triazoles

A general and expeditious approach for the metal-free mediated synthesis of 1,3,5-trisubstituted 1,2,4-triazoles from hydrazones and aliphatic amines has been achieved under aerobic oxidative conditions. The reaction proceeds through a cascade C–H functionalization, double C–N bonds formation, and oxidative aromatization sequence

PdCl₂-Catalyzed Oxidative Cycloisomerization of 3-Cyclopropylideneprop-2-en-1-ones

A novel PdCl₂-catalyzed oxidative cycloisomerization of 3-cyclopropylideneprop-2-en-1-ones, providing a facile synthesis of highly strained functionalized 2-alkylidenecyclobutanones via furan-fused cyclobutene intermediates, is reported. An interesting route to 2(3<i>H</i>)-furanones with a spiro-cyclopropane unit from the obtained 2-alkylidenecyclobutanones via a ring-contraction rearrangement reaction is also realized

Solvent-Controlled, Tunable Hydrosulfonylation of 3‑Cyclopropylideneprop-2-en-1-ones

An interesting and tunable hydrosulfonylation of 3-cyclo­propylidene­prop-2-en-1-ones with sodium sulfinates and acetic acid is described. The corresponding β- or γ-addition products can be produced in good to excellent yields with high selectivities, respectively. A rationale for these transformations is proposed base on the controlled experiments

Ru-Catalyzed Synthesis of Dihydrofuroquinolines from Azido-cyclopropyl Ketones

An efficient Ru-catalyzed synthesis of dihydrofuroquinolines from azido-cyclopropyl ketones via the reduction–cyclization–rearrangement process is reported. A plausible reaction mechanism for this process is depicted. Additionally, when the reaction was carried out under H₂ (1 atm) in the presence of Pd/C, 4-quinolones were obtained in excellent yields

Oxidative Asymmetric [2 + 3] Annulation of Aldehydes with Azomethine Imines Enabled by <i>N</i>‑Heterocyclic Carbene Catalysis

An efficient asymmetric [2 + 3] annulation of simple aldehydes with <i>N</i>,<i>N</i>′-cyclic azomethine imines via oxidative <i>N</i>-heterocyclic carbene (NHC) catalysis is disclosed, affording bicyclic pyrazolidinones bearing two vicinal tertiary stereogenic centers with moderate to good yields (56–84% for 19 examples), good to excellent diastereoselectivities (>20:1 for 17 examples), and good to excellent enantioselectivities (66–98% for 19 examples). This direct α-carbon functionalization reaction of aldehyde can be readily performed on gram scale under mild conditions, and a five-membered transition state is proposed to rationalize the stereochemical outcome