Gold-Catalyzed Cyclization of 3‑(2′-Azidoaryl)-1-arylpropargyl Carbonates or 3‑Aryl-1-(2′-azidoaryl)propargyl Carbonates to Produce Quinolines

A gold-catalyzed cyclization of 3-(2′-azidoaryl)-1-arylpropargyl carbonates to generate substituted quinolines via a sequence of 3,3-rearrangement, 6-<i>endo</i>-trig cyclization and denitrogenation has been developed. Similar products could be obtained from 3-aryl-1-(2′-azidoaryl)­propargyl carbonates under different gold catalytic conditions via a sequential 6-<i>endo</i>-dig cyclization, denitrogenation, and 1,2-H shift process

Gold-Catalyzed Cyclization of 3‑(2′-Azidoaryl)-1-arylpropargyl Carbonates or 3‑Aryl-1-(2′-azidoaryl)propargyl Carbonates to Produce Quinolines

A gold-catalyzed cyclization of 3-(2′-azidoaryl)-1-arylpropargyl carbonates to generate substituted quinolines via a sequence of 3,3-rearrangement, 6-<i>endo</i>-trig cyclization and denitrogenation has been developed. Similar products could be obtained from 3-aryl-1-(2′-azidoaryl)­propargyl carbonates under different gold catalytic conditions via a sequential 6-<i>endo</i>-dig cyclization, denitrogenation, and 1,2-H shift process

Chemo- and Regioselective Assembly of Polysubstituted Pyridines and Isoquinolines from Isocyanides, Arynes, and Terminal Alkynes

We have disclosed a general and efficient synthetic strategy for polysubstituted pyridines and isoquinolines with high chemo- and regioselectivity. In this methodology, 1-alkynyl imines act as the key compound to undergo a sequential alkynyl imine–allenyl imine isomerization/aza-Diels–Alder reaction/aromatization. In the first place, 1-alkynyl imines were formed in situ by a highly selective multicomponent reaction of isocyanides, arynes, and terminal alkynes and reacted with another molecule of arynes or terminal alkynes to furnish target heterocyclic products in a highly efficient and atom-economic manner. On the other hand, we attempted to prepare 1-alkynyl imines by other approaches to undergo a similar reaction sequence to afford polysubstituted pyridines and isoquinolines with a wider range. Different from the first approach, the second approach utilized the preprepared 1-alkynyl imines to introduce the related different substitutents into the final products: arynes or terminal alkynes bearing substituents different from those of 1-alkynyl imines have been successfully applied for the synthesis a wide variety of pyridines and isoquinolines with diversity

Gold-Catalyzed Cyclization of 3‑(2′-Azidoaryl)-1-arylpropargyl Carbonates or 3‑Aryl-1-(2′-azidoaryl)propargyl Carbonates to Produce Quinolines

A gold-catalyzed cyclization of 3-(2′-azidoaryl)-1-arylpropargyl carbonates to generate substituted quinolines via a sequence of 3,3-rearrangement, 6-<i>endo</i>-trig cyclization and denitrogenation has been developed. Similar products could be obtained from 3-aryl-1-(2′-azidoaryl)­propargyl carbonates under different gold catalytic conditions via a sequential 6-<i>endo</i>-dig cyclization, denitrogenation, and 1,2-H shift process

Chemo- and Regioselective Assembly of Polysubstituted Pyridines and Isoquinolines from Isocyanides, Arynes, and Terminal Alkynes

We have disclosed a general and efficient synthetic strategy for polysubstituted pyridines and isoquinolines with high chemo- and regioselectivity. In this methodology, 1-alkynyl imines act as the key compound to undergo a sequential alkynyl imine–allenyl imine isomerization/aza-Diels–Alder reaction/aromatization. In the first place, 1-alkynyl imines were formed in situ by a highly selective multicomponent reaction of isocyanides, arynes, and terminal alkynes and reacted with another molecule of arynes or terminal alkynes to furnish target heterocyclic products in a highly efficient and atom-economic manner. On the other hand, we attempted to prepare 1-alkynyl imines by other approaches to undergo a similar reaction sequence to afford polysubstituted pyridines and isoquinolines with a wider range. Different from the first approach, the second approach utilized the preprepared 1-alkynyl imines to introduce the related different substitutents into the final products: arynes or terminal alkynes bearing substituents different from those of 1-alkynyl imines have been successfully applied for the synthesis a wide variety of pyridines and isoquinolines with diversity

Dual-Modal Colorimetric/Fluorescence Molecular Probe for Ratiometric Sensing of pH and Its Application

As traditional pH meters cannot work well for minute regions (such as subcellular organelles) and in harsh media, molecular pH-sensitive devices for monitoring pH changes in diverse local heterogeneous environments are urgently needed. Here, we report a new dual-modal colorimetric/fluorescence merocyanine-based molecular probe (CPH) for ratiometric sensing of pH. Compared with previously reported pH probes, CPH bearing the benzyl group at the nitrogen position of the indolium group and the phenol, which is used as the acceptor for proton, could respond to pH changes immediately through both the ratiometric fluorescence signal readout and naked-eye colorimetric observation. The sensing process was highly stable and reversible. Most importantly, the suitable p<i>K</i>_a value (6.44) allows CPH to presumably accumulate in lysosomes and become a lysosome-target fluorescent probe. By using CPH, the intralysosomal pH fluctuation stimulated by antimalaria drug chloroquine was successfully tracked in live cells through the ratiometric fluorescence images. Additionally, CPH could be immobilized on test papers, which exhibited a rapid and reversible colorimetric response to acid/base vapor through the naked-eye colorimetric analysis. This proof-of-concept study presents the potential application of CPH as a molecular tool for monitoring intralysosomal pH fluctuation in live cells, as well as paves the way for developing the economic, reusable, and fast-response optical pH meters for colorimetric sensing acid/base vapor with direct naked-eye observation

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