Decarboxylative Conjunctive Cross-coupling of Vinyl Boronic Esters using Metallaphotoredox Catalysis

The synthesis of complex alkyl boronic esters through conjunctive cross-coupling of vinyl boronic esters with carboxylic acids and aryl iodides is described. The reaction proceeds under mild metallaphotoredox conditions and involves an unprecedented decarboxylative radical addition/cross-coupling cascade of vinyl boronic esters. Excellent functional-group tolerance is displayed, and application of a range of carboxylic acids, including secondary α-amino acids, and aryl iodides provides efficient access to highly functionalized alkyl boronic esters. The decarboxylative conjunctive cross-coupling was also applied to the synthesis of sedum alkaloids.     

Divergent,Stereospecific Mono- and Difluoromethylation of Boronic Esters

There is considerable interest in incorporating fluorine into agrochemicals and pharmaceuticals to improve their biological properties. Whilst a number of methods have been reported for installing CH₂F and CHF₂ groups, they are mainly limited to radical reactions, which are invariably racemic. Herein, we report the divergent, stereospecific reaction of fluoroiodomethyllithium with boronic esters to give α-fluoro-boronic esters. These unique intermediates can be readily transformed into the corresponding mono- or difluoromethylated compounds through proto- or fluorodeboronation, respectively. The use of the highly unstable fluoroiodomethyllithium was key to allowing rapid 1,2-migration over competing decomposition of the carbanion. DFT calculations informed and supported the experimental findings.     

Chaos synchronization and transmission of information in coupled SC-CNN-based canonical Chua’s circuit

In this paper, an experimental implementation of State Controlled Cellular Neural Network (SC-CNN)-based canonical Chua’s circuit is presented. Two such electronic circuits are realized. One of the circuits is configured as driver or transmitter, and other circuit is configured as response or receiver system. Synchronization of chaos between the driver and the driven system is demonstrated. The conditions under which complete synchronization is ensured are derived by applying a strategy based on the Master Stability Function and Lyapunov function. We show that transmitter and receiver systems consisting of cascaded SC-CNN-based canonical Chua’s oscillator can synchronize when they are coupled using direct information from the transmitter into the receiver. The communication performances of different information signals such as sinusoidal, square, and speech signals are demonstrated by real-time hardware experiments. The experimentally observed results are in agreement with the numerically obtained results, and they closely match with each other.     

Study of Intermetallic Growth and Kinetics in Fine-Pitch Lead-Free Solder Bumps for Next-Generation Flip-Chip Assemblies

With continued advances in microelectronics, it is anticipated that next-generation microelectronic assemblies will require a reduction of the flip-chip solder bump pitch to 100 μm or less from the current industrial practice of 130 μm to 150 μm. With this reduction in pitch size, and thus in bump height and diameter, the interaction between die pad metallurgy and substrate pad metallurgy becomes more critical due to the shorter diffusion path and greater stress. Existing literature has not addressed such metallurgical interaction in actual fine-pitch flip-chip assemblies. This work studies intermetallic growth and kinetics in fine-pitch lead-free solder bumps through thermal aging of flip-chip assemblies. Based on this study, it is seen that Ni from the die pad diffuses to the substrate pad region and Cu from the substrate pad diffuses to the die pad region, thus the resulting intermetallic compounds at the die and substrate pad regions are influenced by the other pad as well. Such cross-pad interaction is much stronger in fine-pitch solder bumps with smaller standoff height. It is seen that the die pad region contains Ni₃P and (Cu,Ni)₆Sn₅ after thermal aging, while the substrate pad region contains Cu₃Sn and (Cu,Ni)₆Sn₅. By digitally measuring the thickness of the interfacial phases, the kinetics parameters and the activation energy were calculated for the growth of (Cu,Ni)₆Sn₅ on the substrate side. The Cu diffusion coefficient through the intermetallic compound (IMC) layer was found to be 0.03370 μm²/h, 0.1423 μm²/h, and 0.4463 μm²/h at 100°C, 125°C, and 150°C, respectively, and the apparent activation energy for the growth of compound layers was 67.89 kJ/mol.     

A very high performance self-biased cascode current mirror for CMOS technology

This paper presents a novel high performance self-biased cascode current mirror (CM) for CMOS technology. The proposed circuit shows a resistance compensated high bandwidth CM operating at low voltages. This circuit uses super cascode configuration to obtain high output impedance required for high performance of CM. Active implementation of passive resistances of the proposed circuit is shown. The simulations of proposed CM are carried out by Mentor Graphics Eldospice based on TSMC 0.18 μm CMOS technology, for input current range of 0–500 μA. A bandwidth of 2.26 GHz, input and output resistances of 679 Ω and 482 MΩ respectively, are obtained with a single supply voltage of ?1 V.     

Linear and nonlinear stability of double diffusive convection in a couple stress fluid–saturated porous layer

The linear and nonlinear stability of double diffusive convection in a layer of couple stress fluid–saturated porous medium is theoretically investigated in this work. Applying the linear stability theory, the criterion for the onset of steady and oscillatory convection is obtained. Emphasizing the presence of couple stresses, it is shown that their effect is to delay the onset of convection and oscillatory convection always occurs at a lower value of the Rayleigh number at which steady convection sets in. The nonlinear stability analysis is carried out by constructing a system of nonlinear autonomous ordinary differential equations using a truncated representation of Fourier series method and also employing modified perturbation theory with the help of self-adjoint operator technique. The results obtained from these two methods are found to complement each other. Besides, heat and mass transport are calculated in terms of Nusselt numbers. In addition, the transient behavior of Nusselt numbers is analyzed by solving the nonlinear system of ordinary differential equations numerically using the Runge–Kutta–Gill method. Streamlines, isotherms, and isohalines are also displayed.     

Total synthesis of isofregenedadiol

The first total synthesis of isofregenedadiol, a bicyclic diterpene isolated from H. Viscosum, is reported starting from a D-(-)-pantolactone chiral pool. A one-pot quadruple reaction sequence comprising an enyne ring-closing metathesis/cross-metathesis/Diels-Alder/aromatization for the construction of a target skeleton is the highlight of the present synthesis.     

Simultaneous determination of bioactive compounds in Piper nigrum L. and a species comparison study using HPLC-PDA

Piper nigrum L. is a traditional medicine widely used in India for illnesses such as constipation, diarrhoea, earache, gangrene, heart disease, hernia, hoarseness, indigestion, insect bites, insomnia, joint pain, liver problems, lung disease, oral abscesses, sunburn, tooth decay and toothaches. In this study, six bioactive compounds, namely piperine (1), pellitorine (2), guineensine (3), pipnoohine (4), trichostachine (5) and piperonal (6) were quantified in different extracts of P. nigrum L. and compared with those of P. longum L. and P. chaba Hunter. To evaluate the quality of P. nigrum, a simple, accurate and precise HPLC-PDA method was developed for the simultaneous determination of the above-mentioned six compounds. The separation was achieved by Phenomenex Luna RP C(18) column (150?×?4.6?mm, 5?μm, Phenomenex Inc, CA, USA) with a binary gradient solvent system of water-acetonitrile, at a flow rate of 1.0?mL?min(-1) and detected at 210, 232, 262 and 343?nm. All six calibration curves showed good linearity (R (2)?>?0.9966). The method was reproducible with intra- and inter-day variations of less than 2% and 5%, respectively. The results demonstrated that this method is simple, reliable and suitable for the quality control of these plants.     

Antinociceptive activity and acute toxicity study of Flaveria trinervia whole plant extracts using mice

The antinociceptive activity of Flaveria trinervia extracts by tail-flicking and writhing methods was evaluated using mice. The abdominal writhing method was carried out by administering petroleum ether, chloroform and methanol extracts orally. After 1?h of incubation, 0.6% acetic acid (10?mL?kg(-1)) was administered intraperitoneally. After 5?min, each group of mice was observed for the amount of writhing for a duration of 20?min. Acetyl salicylic acid was used as the standard reference. The tail-flick method was carried out using a thermal model and the maximum possible analgesia was calculated. The LD?? values of petroleum ether, chloroform and methanol extracts were 700, 700 and 500?mg?kg?1, respectively. The methanol extract at 50?mg?kg?1 showed significant antinociceptive activity. The petroleum ether and chloroform extracts showed moderate antinociceptive activity at a dose of 70?mg?kg?1. The methanol extract showed more significant antinociceptive activity than the other extracts but was less effective than the standard. This investigation finds support for the ethnomedicinal claims of F. trinervia.