Photoinduced [3+2] Cycloaddition of Carbenes and Nitriles: A Versatile Approach to Oxazole Synthesis

We have developed a photoinduced protocol for the synthesis of pharmaceutically important oxazole molecules using diazo- and nitrile-containing reactants. The process involves the initial photolysis of the diazo compound to afford singlet carbenes, which are tapped by nitriles in a [3+2] cycloaddition fashion to give substituted oxazoles. With di-nitrile compounds, useful bis-oxazoles were obtained. The applicability of the transformation is showcased through the expedient synthesis of small-molecule drugs and biologically relevant molecules such as felbinac, pimprinine, texamine, ugnenenazole etc. The protocol is also useful for the generation of ²H and ¹³C isotope labelled oxazoles. Merging photolysis with continuous-flow chemistry was demonstrated for scaling up the reaction. The non-requirement of metal catalysis or photosensitizers to harness the light energy with blue light sufficing the execution of the reaction makes it a versatile and general protocol for the synthesis of structurally diverse oxazoles     

Copper Catalyzed Oxidative Esterification of Aldehydes with Alkylbenzenes via Cross Dehydrogenative Coupling

Copper(II) as the catalyst in a cross dehydrogenative coupling (CDC) reaction has been demonstrated for the synthesis of benzylic esters using aldehydes and alkylbenzenes as coupling partners.     

Effect of water during the quantitation of formate in photocatalytic studies on CO2 reduction in dimethylformamide

The effect of the water concentration on the quantitation of formate from dimethylformamide in the presence of electron-donating bases using ion chromatography is reported. This observation has important implications in the area of the photocatalytic reduction of CO(2), where formate levels are often used to calculate catalyst turnover numbers.     

A new colorimetric chemodosimeter for mercury ion via specific thioacetal deprotection in aqueous solution and living cells

A sensitive and selective new chemodosimeteric chemosensor (DIBT) for mercury ions was successfully devised and characterized. Upon addition of Hg²⁺ to DIBT, a red-edge absorption band at 972 nm was observed. An important feature for the new chemodosimeter is its high selectivity toward mercury ions over the other competitive species due to Hg²⁺-triggered specific C–S cleavage, making the ‘naked-eye’ detection of mercury ions possible in aqueous solution and living cells such as Candida albicans.     

Some insights on the recent spate of accidents in Indian Railways

Indian Railways (IR), the largest rail passenger carrier in the world, has experienced 11 major accidents due to derailment or collision between trains in the year 2010, leading to several human casualties and large-scale disruptions in traffic. Alarmingly, 8 of these 11 accidents have occurred within a specific geographical region known as the Indo-Gangetic plain. In order to identify the general causes of such frequent accidents, and the specific factors leading to repeated accidents in a particular region, we systematically collect and analyze data of IR traffic over the last two decades. We find that there has been an unbalanced growth in IR traffic in the Indo-Gangetic plain over the last two decades, and consequently most of the high-traffic rail-routes presently lie in this region. However, construction of new tracks and train-routes has been nominal compared to the increase in traffic, leading to frequent congestion and over-utilization of existing tracks. Modeling the traffic-flow using computer simulations, we also show that if all trains were to travel in accordance with the IR schedule, the present infrastructure would be insufficient to handle the resultant traffic-flow in some of the high-traffic routes. Hence this study reflects some of the inherent problems in the scheduling of trains and evolution of IR, and also identifies several regions where traffic is likely to exceed safe limits.