1.3. An Overview for the Synthesis of Tetrahydropyrans, Piperidines and Dihydro-γ-pyrone Derivatives To build this class of heterocycles, many strategies have been developed over the years. The most widely used methods are the Prins cyclization, hetero-Diels–Alder (HDA) cyclization, oxonium-ene cyclization, the intramolecular Michael additions and ring-closing metathesis. Other strategies include electrophile-induced cyclizations of non-activated alkenes and Lewis acid promoted cyclizations of epoxy alcohols/amines. Reported methods used for six membered oxygen and nitrogen ring synthesis have their own advantages and disadvantages. Therefore, development of new and efficient methods is imperative especially to address the issue of diastereoselectivity. Among these methods stated, this thesis mainly discusses Prins, aza-Prins cyclization and HDA reactions in detail for the construction of six membered O- and N- heterocycles. 1.3.1. Prins Cyclization Reaction In 1919 a Dutch chemist H. J. Prins has first reported …show more content…
In detail, the Prins cyclization of homoallylic amines takes place in a fashion similar to that of homoallylic alcohols, whereby the non bonding electrons on the nitrogen initiate the sequence of reaction steps by attacking the electrophilic site of the aldehyde activated by an acid catalyst. The key intermediate of the aza-Prins cyclization is an iminium ion, in analogy to the oxonium ion. Compared to classical Prins cyclization, examples of aza-Prins cyclization using iminium ions leading to nitrogen-containing heterocycles have been less developed in the literature due to less electrophilic nature of iminium ions compared to oxo-carbenium ions. Whereas, aza-Prins cyclization of acyclic/cyclic N-acyliminium ion intermediates to achieve piperidine ring containing mono and bicyclic compounds is well explored due to more electrophilic nature of N-acyliminium
Linus Pauling Linus Pauling was a very important scientist who over seven decades of his life made many discoveries in multiple fields of science including: physical, structural, analytical, inorganic, organic chemistry, and biochemistry. He was born in the 20th century and contributed greatly to science field during this time. He is known for “Pauling’s Rules” and other inventions he is responsible for. He would also go on to write his own books detailing some of his work, he made very diverse discoveries and discovered many things in many different fields; which is very unique for a scientist. Pauling was an activist and was very involved and fought for causes he thought were important.
Experiment # 3 – Resolution Of ( )- -Phenylethylamine Name: Krishna Binu Class: Chem 2020 Due Date: October 23, 2015 Table 1 Shows the experimental results. Name Result Mass of Amine (g) 3.32 Mass of Salt (g) 1.26 Observed Rotation of Isolated Amine (Degrees) -36.33 1) Draw the chemical structures of the two diastereomeric salts produced in Part A using a proper perspective (line-angle) representation.
Benzyne Formation and the Diels-Alder Reaction Preparation of 1,2,3,4 Tetraphenylnaphthalene Aubree Edwards Purpose: 1,2,3,4-tetraphenylnaphthalene is prepared by first producing benzyne via the unstable diazonium salt. Then tetraphenylcyclopentadienone and benzyne undergo a diels-alder reaction to create 1,2,3,4-tetraphenylnaphthalene. Reactions: Procedure: The reaction mixture was created. Tetraphenylcyclopentadienone (0.1197g, 0.3113 mmol) a black solid powder, anthranilic acid ( 0.0482g, 0.3516 mmol) a yellowish sand, and 1,2-dimethoxyethane (1.2 ml) was added to a 5-ml conical vial.
It was first described in 1769 by a german zoologist name Peter simon
This discovery has improved many lives and was huge advancement in the pharmacological world. Pharmaceutical Innovations that Resulted from the Discovery (e.g. improved drugs that subsequently became
There have also been tests done with thimerosal in 1930 on people with a disease and
Yale scientists Dr. Allan C. Steere and Dr. Stephen E. Malawista are credited as being the first to recognize, name, characterize,
Some major ones include better syringes, more accurate thermometers, using laughing gas for medical treatments, and the ophthalmoscope. Syringes have been around for a long time, however, the last adjustment was made in 1853, when Alexander Wood introduced the hypodermic method (Duin). Thermometers also were developed to where they were much faster, efficient, smaller, and more accurate in 1867 by Sir Thomas Clifford Allbutt (Duin). However, two of the most important inventions were laughing gas for medical procedures and an ophthalmoscope. Nitrous oxide, also known as laughing gas, was first discovered in 1772 (Walton).
Fortunately, about ten years later, two scientists, Howard Florey and Ernst Chain, found Fleming’s article. In 1940 they tested the drug on mice and discovered
In doing this, they found that a plutonium-organic hybrid compound that Albrecht-Schmitt and his team had created, behaved like other compounds that were made up of lighter elements! Thomas claimed that what made the discovery so surprising to him was that the material that was created was “...really, really simple”. He realized that he can make that same class of compound with other types of heavy elements as
While electroluminescence as a phenomenon was found in 1907 by the British experimenter H. J. Round of Marconi
Whöler also, with Liebig, discovered the concept of isomers. Lastly, he paved the way for the disapproval of the
Cyclopropane is a flammable, synthetic compound which is a ring made up of three carbon atoms. Each carbon atom has two stereoselective hydrogens thus creating a molecular formula of C3H6. Cyclopropane is seen in daily life through physiological activity and in chemical and biological transformations. Cyclopropanols are versatile building blocks for organic synthesis because of the ability to undergo various transformation. The unique ring structure, that involves an -OH group, allows for many opportunities for drug design in today’s pharmaceutical field, especially in antibiotics.
Synthetic molecules and their impact on technology and our daily life Name: jeena Grade: 9A Teachers name: Bader Saidi Unit title: how do atoms bond? Introduction: Innovation is the result of a need, a demand, and to solve an issue or a problem. This allowed scientists over the years, not only study natural elements and well known compounds, but led them to form various chemical reactions to produce new products; synthetic products that will serve their need. I chose this topic to explore and recognize manufactured synthetic products, their uses, applications and their impact on the environment.