One-pot,four-component synthesis of novel biologically important indeno[2,3-b]quinoxaline]-3-carbonitriles in fluoro-alcohols under ultrasound irradiation

Research on Chemical Intermediates - We have reported trifluoroethanol (TFE) as an efficient and recyclable medium in promoting one-pot, four-component synthesis of biologically and...     

Synthesis of new 4,6-diaryl-2-(arylthio)nicotinonitriles in Triton X-100 aqueous micellar media

In this communication,we report four component condensations of acetophenone,arylaldehydes,arylthiol,and malononitrile in the presence of Triton X-100（5 mol%） aqueous micelles.This reaction led to the formation of 4,6-diaryl-2-（arylthio）nicotinonitrile new derivatives in good yields.The FT-IR,¹⁹F NMR,¹H NMR,¹³C NMR spectra and elemental analysis confirm the structure of compounds.     

Continuous oxygen monitoring of mammalian cell growth on space shuttle mission STS-93 with a novel radioluminescent oxygen sensor

A compact, flow-through oxygen sensor device based on luminescence quenching was used to monitor dissolved oxygen levels during mammalian cell growth on the STS-93 mission of the Columbia space shuttle. Excitation of an oxygen-sensitive ruthenium complex was provided by a radiolumin escent light source (0.9 mm in diameter, 2.5 mm long), and the intensity of the resulting luminescence was measured by a simple photodiode detector. The use of radiolum inescence for the excitation light source is a unique approach that provides many features important for long-term and remote monitoring applications. For the spaceflight experiment, human lung fibroblast cells (WI-38) were grown in hollow-fiber bioreactors. Oxygen concentration was measured in the flow path both before and after the bioreactor cartridge in order to gain information about the metabolism of the cells. The sensor was found to be nonperturbing to cell growth and withstood the challenging physical conditions of shuttle launch and landing while maintaining a stable calibration function. In addition, the sensor provided physically meaningful oxygen predictions.     

Wireless Network Optimization for Federated Learning with Model Compression in Hybrid VLC/RF Systems

In this paper, the optimization of network performance to support the deployment of federated learning (FL) is investigated. In particular, in the considered model, each user owns a machine learning (ML) model by training through its own dataset, and then transmits its ML parameters to a base station (BS) which aggregates the ML parameters to obtain a global ML model and transmits it to each user. Due to limited radio frequency (RF) resources, the number of users that participate in FL is restricted. Meanwhile, each user uploading and downloading the FL parameters may increase communication costs thus reducing the number of participating users. To this end, we propose to introduce visible light communication (VLC) as a supplement to RF and use compression methods to reduce the resources needed to transmit FL parameters over wireless links so as to further improve the communication efficiency and simultaneously optimize wireless network through user selection and resource allocation. This user selection and bandwidth allocation problem is formulated as an optimization problem whose goal is to minimize the training loss of FL. We first use a model compression method to reduce the size of FL model parameters that are transmitted over wireless links. Then, the optimization problem is separated into two subproblems. The first subproblem is a user selection problem with a given bandwidth allocation, which is solved by a traversal algorithm. The second subproblem is a bandwidth allocation problem with a given user selection, which is solved by a numerical method. The ultimate user selection and bandwidth allocation are obtained by iteratively compressing the model and solving these two subproblems. Simulation results show that the proposed FL algorithm can improve the accuracy of object recognition by up to 16.7% and improve the number of selected users by up to 68.7%, compared to a conventional FL algorithm using only RF.     

Linear dependence among Siegel modular forms

Theorems are given which describe when high enough vanishing at the cusps implies that a Siegel modular cusp form is zero. Formerly impractical computations become practical and examples are given in degree four. Vanishing order is described by kernels, a type of polyhedral convex hull. Received: November 19, 1998 / Revised: July 5, 1999 / Published online: September 5, 2000     

An efficient fluorination of β-ketosulfones promoted by a room-temperature ionic liquid at ambient conditions under ultrasound irradiation using Selectfluor~(TM) F-TEDA-BF_4

<正>The fluorination reaction involving aβ-ketosulfones by Selectfluor~(TM) was efficiently promoted by the ionic liquid,[Hbim]BF_4 (EL) as a reaction medium with methanol as co-solvent at room temperature under ultrasonic irradiation to afford the corresponding mono and difluoro-β-ketosulfones in excellent yields.The advantages of this method include among others the use of a recyclable, non-volatile ionic liquid,which promotes this protocol under room temperature without the requirement of any added catalyst under ultrasonic irradiation.     

An efficient synthesis of quinolines derivatives promoted by a room temperature ionic liquid at ambient conditions under ultrasound irradiation via the tandem addition/annulation reaction of o-aminoaryl ketones with α-methylene ketones

The condensation reaction involving an o-aminoaryl ketones with α-methylene ketones via the tandem addition/annulation reaction by the ionic liquid of [Hbim][BF₄] (IL) as a solvent with methanol as co-solvent at room temperature under ultrasound irradiation afforded the corresponding quinolines derivatives in excellent yields. The use of ionic liquid and ultrasound, which promoted this protocol under room temperature without the requirement of any added catalyst. Quinoline derivatives are important and have a potential use as special biological drug in medicine.     

Molecular simplification in bioactive molecules: formal synthesis of (+)-muconin

The concept of molecular simplification as a drug design strategy to shorten synthetic routes, while keeping or enhancing the biological activity of the lead drug, has been applied to (+)-muconin, an acetogenin with remarkable cytotoxicity. A novel approach that enables the stereoselective synthesis of such a natural compound or its enantiomer from a common precursor is described. An additional advantage of the method is complete stereochemical control and the decrease in the number of chemical steps required, thus providing an enhancement of the overall yield. Antiproliferative studies against the human solid tumor cell lines showed that the aliphatic chain-THF/THP fragment of (+)-muconin has modest cytotoxic activity. The strategy opens the way to preparing novel bioactive acetogenin analogues by shorter synthetic routes.     

Heteroatom Effects on Singlet–Triplet Energy Gaps of Divalent Five-Membered Ring X2C2H2C (X = N,P, As,and Sb)

Thermal energy gaps, ΔE_s–t; enthalpy gaps, ΔH_s–t; and Gibbs free energy gaps, ΔG_s–t between the singlet (s) and triplet (t) states of X₂C₂H₂C, 1_X (X = CH, N, P, As, and Sb) were calculated and compared with those analogues, XC₂H₃C, 1′_X (X = N, P, As, and Sb) at the B3LYP/6-311++G** level of theory. Density functional theory (DFT) calculations indicated that the ΔG_s-t, for 1_X (X = N and P) should be lower with respect to their monosubstituted 1′_X . In contrast, the ΔG_s-t for 1_X (X = As and Sb) should be larger with respect to 1′_X . The ΔG_s-t for 1_X and 1′_X were increased in the following order: 1_Sb > 1_As > 1_C > 1_P > 1_N ; 1′_Sb > 1′_As > 1′_P > 1_C > 1′_N , respectively.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Selectfluor™ promoted synthesis of 9-aryl-1,8-dioxooctahydroxanthane derivatives under solvent-free conditions

A novel and efficient procedure for the synthesis of 1,8-dioxo-octahydro-xanthenes through one-pot condensation of 5,5- dimethyl-1,3-cyclohexadione with aryl aldehydes in the presence of selectfluor? [1-(chloromethyl)-4-fluoro-1,4- diazoniabicyclo[2,2,2]octane bis(tetrafluoroborate) as catalyst under solvent free conditions was applied. It demonstrated several advantages such as good yields of products, simple operation, convenient separation, and inexpensive catalyst.