Studies in reaction path synthesis

Engineering in Life Sciences, 2006

The need for more selective reactions steps and the compatibility between process steps which follow on from each other has been a major driving force for organic synthesis. The synthesis of chiral compounds, metabolites, new chemical entities and natural products by a combination of chemical and enzyme reaction steps has become well established, due the existence of stable enzymes as selective catalysts which are inherently chiral by nature. Auxiliary tools such as suitable transfer reagents for reaching complete conversion, easy and robust reaction control as well as tools for straightforward workup and purification of the final product have been developed. Selective enzyme reaction steps in the area of hydrolyses, oxidation steps including hydroxylation and the Baeyer-Villiger oxidation, carbon-carbon bond formation and glycosylation reactions have compared favorably with existing methods of classical organic synthesis. The tools developed during optimization and scale-up of these enzyme reaction steps have the potential to shorten development time. The introduction of selective enzyme reactions into an entire synthetic process has resulted in harmonization of improvements in economic efficiency with resultant solutions to health, safety and environment problems. This will become even more important in industrial synthetic chemistry in the future, for convenient solutions to certain intractable synthetic problems and for expanding the repertoire of chemistry by modular biocatalysts. Efficient isolation procedures for the final product are essential to take full advantage of the biocatalytic conversion to obtain high product yields.

Canadian Journal of Chemistry

Chemistry has always had as a target the conversion of molecules into valuable materials. Nevertheless, the aim of past synthesis has primarily focused on achieving a given transformation, regardless of the environmental impact of the synthetic route. Given the current global situation, the demand for sustainable alternatives has substantially increased. Our group focuses on developing selective chemical transformations that benefit from mild conditions, improved atom economy, and that can make use of renewable feedstocks as starting materials. This account summarizes our work over the past two decades specifically regarding the selective removal, conversion, and addition of functional groups that can, later on, be applied at a late stage for the modification of complex molecules.

In chemistry, chemical synthesis is a purposeful execution of chemical reactions to obtain a product, or several products. This happens by physical and chemical manipulations usually involving one or more reactions. In modern laboratory usage, this tends to imply that the process is reproducible, reliable, and established to work in multiple laboratories

Angewandte Chemie International Edition in English, 1993

2017

Essential industrial processes may threaten the environment despite the restrictions on the standards of rejections. Preserving a safe environment remains a major concern. Industry must look for new technologies, known as “clean” to reduce the environmental impact of their production activities and the consumption of energy and raw materials; This would require following an ecological and durable chemistry known as green chemistry. The objective of this present work is an initiation with the application of the principles of green chemistry through the calculation of various parameters, namely: carbon efficiency, atom economy, environmental factor, reaction mass efficiency, material recovery parameter, etc. The work shows the importance of green chemistry principles in searching for a more “clean” reaction way for a given synthesis or production. Indeed, between substitution and addition reaction mechanisms to synthesize tertiobutyl chloride, the results show that the second one prov...

Catalysts

Multicomponent reactions (MCRs) have been gaining significance and attention over the past decade because of their ability to furnish complex products by using readily available and simple starting materials while simultaneously eliminating the need to separate and purify any intermediates. More so, most of these products have been found to exhibit diverse biological activities. Another paradigm shift which has occurred contemporarily is the switch to heterogeneous catalysis, which results in additional benefits such as the reduction of waste and an increase in the safety of the process. More importantly, it allows the user to recover and reuse the catalyst for multiple runs. In summary, both methodologies adhere to the principles of green chemistry, a philosophy which needs to become overarchingly enshrined. The plethora of reactions and catalysts which have been developed gives hope that chemists are slowly changing their ideology. As a result, this review attempts to discuss mult...

Endeavour, 1994

Traditionally, organic syntheses are effected by a sequence of reactions between two components: one consequence of this is that final yields can be very low. It has long been known, however, that effective syntheses can be carried out using three, or sometimes more, reactants simultaneously and a few such processes are used industrially. In recent years processes of this kind have been systematically investigated using sophisticated computer techniques, and successful syntheses have been achieved using as many as seven components. In chemical reactions, usually only one or two chemical compounds participate. Onepot reactions that form products from three or more different starting compounds are called multicomponent reactions (MCRs). The reagents may be different individual molecules or they may be different functional groups of the same reagent. One-pot reactions are often also called domino reactions or tandem reactions. MCRs may be older than life. It is assumed, that adenine 2-one of the nitrogenous bases of DNA and RNA-prebiotically originates from five molecules of hydrogen cyanide [1]-[3] (figure 1). Note that each one of those five molecules plays a different role. Syntheses of complex organic compounds are usually effected step by step from many starting materials. However, there are also impressive cases of organic syntheses that create complex chemical products in a single polyfunctional one-pot operation (figure 2). R. B. Woodward's famous synthesis of strychnine [4] was carried out in 28 steps and had a overall yield of 0.3 per cent. In contrast, the complex one-step reaction 4-5 performed by C. H. Heathcock et al. [5] is very impressive in that the daphni-Ivar Ugi, Dr. ret. nat. Was born in Estonia in 1930 and studied chemistry, and simultaneously pure mathematics, at the University of Tfibingen. After taking his doctorate at Munich he joined Bayer A.G. at Leverkusen, latterly as research director. In 1968 he became professor of chemistry at the University of Southern California, and since 1971 at the Technical University of Munich ('rUM). He has developed new preparative methods and participated in mathematical, logical, and computer-aided developments in chemistry.

Journal of The American Chemical Society, 1974

A major extension has been made to the computer program (L H A S A) being developed to assist chemists in synthetic analysis. This extension allows the automatic processing of a target molecular structure in the antithetic (retrosynthetic) direction with a depth of search corresponding to as many as 15 steps to determine whether a goal of utilizing a specific important ring-forming process can be attained. The method is described for the Diels-Alder transform (retroreaction), the first specific case to be implemented. The search for applicable subgoals leading to the application of the Diels-Alder trans

Virtual Screening: An Alternative or Complement to High Throughput Screening?, 2002

In combinatorial chemistry, hundreds of thousands of reactions are run in parallel, on beads, or simultaneously in solution. A careful planning of these reactions is therefore of paramount importance in order to influence the products obtained in these experiments. We present here three software systems that should assist the chemist in solving problems met in combinatorial chemistry: WODCA can be used for the planning of the synthesis of combinatorial libraries. EROS is designed to model the course of chemical reactions to predict their products. CORA is a tool to analyze series of reactions such as those contained in reaction databases to derive knowledge that can be used in designing and simulating chemical reactions.

1994

Electron Counting Shape of Molecules Acid/Base Characteristics Nucleophilic Substitution Reactions Radical Substitution Reactions Elimination Reactions Molecular Rotations Oxidation Numbers.