New Approaches To Heterocycle Synthesis: A Greener Route To Structurally Complex Protonated Azomethine Imines, And Their Use In 1,3-Dipolar Cycloadditions

1-Aza-2-azoniaallene salts are reactive intermediates that undergo [3+2] cycloaddition with many different types of multiple bonds. For the past several years, the Brewer group has studied the reactivity of these intermediates in intramolecular reactions, and have discovered that these cationic heteroallenes can react through a variety of other, mechanistically distinct, pathways to give different classes of nitrogen heterocycles. For example, prior work in the Brewer group revealed that 1-aza-2-azoniaallene salts could react in an intramolecular [4+2] cycloaddition reaction to give protonated azomethine imine salts containing a 1,2,3,4-tetrahydrocinnoline scaffold. Further study of the scope and limitations of this Diels-Alder-like reaction are described herein. These studies primarily focused on how varying the N-aryl ring and alkene substituents affected the reaction. We discovered that in several instances, the metal mediated reaction did not facilitate the cycloaddition very well, so we searched for alternative ways to facilitate the reaction. We discovered that a non-metallic Lewis acid (TMSOTf) provided very clean products with α-chloroazo compounds. I hypothesized that changing the leaving group adjacent to the azo might further improve the reaction. With this in mind, I developed a technique to prepare α-trifluoroacetoxyazo compounds by treating aryl hydrazones with trifluoroacetoxy dimethylsulfonium trifluoroacetate. This technique is compatible with all types of functional groups including nitro aryl compounds, which gave low yields of the corresponding chloroazo derivatives. Importantly, these α-trifluoroacetoxyazo compounds gave even better cycloaddition results when treated with TMSOTf, and this method is more practical, more environmentally friendly, and greener than the metal mediated technique. This process even returned sterically hindered products in high yield, and provide a dearomatized non-protonated azomethine imine salt, which further verified the proposed mechanism of the [4+2] cycloaddition. Azomethine imines are well known to undergo 1,3-dipolar cycloadditions with alkenes. We wondered if the protonated azomethine imine salts generated by the [4+2] cycloaddition could be used in a subsequent base-mediated [3+2] cycloaddition to generate structurally complex tetra- or pentacyclic products. We were pleased to find that the protonated azomethine imines indeed reacted smoothly with a variety of π-system in the presence of triethylamine to give the corresponding cycloadducts in high yields with moderate to high diastereoselectivities. In an attempt to understand the diastereoselectivity of these [3+2] cycloadditions better, I modeled them computationally

Current Situation and Issues of Continuous Assessment System in Mathematics Education of Nepal

Continuous Assessment System (CAS) is a formative type of student assessment carried out during teaching-learning activities in the classroom. The prime concern of this study is to identify the current situation and issues of CAS in the mathematics classroom, and if there are any issues, to indicate some remedies for them. Seventy-nine primary mathematics teachers and nine instructors were selected as samples. The questionnaires, interviews, observations, and focus-group discussions were used as data collection tools. According to the data analysis, most of the respondents mentioned that in teacher training, there is no time for discussion and practical sessions on how to make a plan and use practically CAS tools in students\u27 evaluation, in other words, how to use students\u27 evaluation information to improve their learning. It was also clarified that most teachers do not use CAS evaluation criteria (tools) and give ticks (score) to their students without any real assessment. Thus, they are possibly not able to use the students\u27 evaluation information to improve their learning. For improving the implementation of CAS in the mathematics classroom, teacher training should be practice-based and focused on how to make a plan of CAS and use its tools for students\u27 assessment and how to use assessment information to improve their learning. The government should encourage all teachers to implement CAS in classroom instruction and provide a favorable environment for teachers to share good practices of CAS

A SCENARIO OF MEDIA AWARENESS FOR SOCIAL NETWORKING

The term media is derived from Medium, which means carrier or mode. Media denotes an item specifically designed to reach a large audience or viewers. The term was first used with the advent of newspapers and magazines. However, with the passage of time, the term broadened by the inventions of radio, TV, cinemas and Internet. Tools for social networking and social awareness are developing rapidly and evolving continuously. They are gaining popularity in a growing number of professional as well as personal activities, including scholarly research. There are social awareness tools for science researchers that facilitate collaboration, help manage references, and offer options for presenting findings in new ways.This paper discusses those tools. Evaluating and understanding their functionalities requires effort, and scientists can be reluctant to invest the necessary time to learn to use and populate them on their own. This suggests that an important role for librarians is to evaluate the many social awareness tools available, to recommend the ones that are best suited to each researcher's needs, and to help researchers use those tools effectively.In the world of today, media has become almost as necessary as food and clothing. It is true that media is playing an outstanding role in strengthening the society. Its duty is to inform, educate and entertain the people. It helps us to know current situation around the world. The media has a strong social and cultural impact upon society. Because of its inherent ability to reach large number of public, it is widely used to convey message to build public opinion and awareness

A Simple Approach for Black Out Problem

Antennas surrounding by the plasma medium does not radiate for all the frequencies but only for those which are greater than the plasma frequency. Here we have proposed a cylindrical (axial magnetized) antenna system which radiates for all frequencies irrespective of plasma frequency and this is the solution for the black-out situation which occurs for certain frequencies

A Review on Bacterial Degradation of Benzo[a]pyrene and Its Impact on Environmental Health

Benzo[a]pyrene is a polycyclic aromatic hydrocarbon (PAH) having a high molecular weight. Benzo[a]pyrene and other PAHs are induces severe acute or chronic human health hazards and are extremely carcinogenic, mutagenic, immunotoxic, and teratogenic. Microorganisms play a crucial part in the degradation of benzo[a]pyrene from polluted environments. Such micro-organisms synthesize monooxygenase and di-oxygenase enzymes that proceed with the aerobic or anaerobic catabolic degradations of benzo[a]pyrene. Bioaugmentation, biomineralization, and biostimulation methods can be used for the decontamination of benzo[a]pyrene from hydrocarbon contaminated sites. In this review paper, we thoroughly explained the impacts of benzo[a]pyrene pollution on human health and the environment. Further, this study also described various pathways regarding the bio-degradation of benzo[a]pyrene and also an updated overview of future prospects of benzo[a]pyrene biodegradation