Modern synthetic chemistry

Metal-assisted enantioselective catalytic reactions are one of the most important areas in organic chemistry [1-3]. They require the appropriate design and the preparation of chiral transition metal complexes, a field also of major importance in modern synthetic chemistry. These complexes are selected on both their ability to catalyze a given reaction and their potential as asymmetric inducers. To fulfill the first function, it is absolutely required that the catalysts display accessible metal coordination sites where reactants can bind since activation would result from a direct interaction between the metal ion... 

Several condensed systems, especially those combined with pyridine rings, show biological activity, e.g., in the field of crop protection and as anti-virus and anti-cancer compounds. Aza-Wittig reactions in particular should make several novel heterocyclic rings available. The aza-Wittig reaction of iminophosphoranes has to be considered as a major principle in modern synthetic chemistry, as was wisely foreseen by Staudinger and Meyer as early as 1919. 

Modern synthetic chemistry has taken up the challenge of acyclic substrate-induced stereoselection302, including auxiliary-directed stereoselectivity. The main principles are 1,2-in-duction, the formation of cyclic intermediates, and intramolecular reactions. Many aspects, rules , and examples of diastereoface-differentiating reactions, both in cyclic and in acyclic systems, are summarized in Section 2.3.5.2. 

Obviously, we owe much to the pioneers of this area and it is a testimony of the importance of their work to find cross-coupling affecting so many areas of chemistry. Much progress has been made in the last decade, and at the look of things much will emerge in the very near future to solidify the crucial importance of metal-mediated cross-coupling in modern synthetic chemistry. 

Organometallic reactions are becoming increasingly important in modern synthetic chemistry, but it is not obvious what the simple reaction dimensions would be into which such real reactions could be analyzed. Even for such a simple reaction as addition of a Grignard reagent to a carbonyl compound there are problems in picking out simple dimensions and defining a detailed... 

Much attention has been devoted in the professional journals and in the press to gasohol, and announcements of new ethanol plants and process improvements seem unending. A perspective on the problems and promise of gasohol is covered along with a status report on work in Brazil on (fuel) methanol from wood, not by destructive distillation used in the past, but by modern synthetic chemistry. Other promising new uses for... 

In modern synthetic chemistry, the advantages of zinc were rediscovered. New selective reactions illustrated below were found, together with an unexpected possibility of performing some condensations in aqueous media. 

Both esterification and transesterification are classical reactions that still find great demands in modern synthetic chemistry.258,259 1,3-Disubstituted tetrakis(fluoroalkyl) distannoxanes, (XR2SnOSnR2Y)2 (R = C6Fi3C2H4 and... 

Transition metal enantioselective catalysis is among the most challenging and widely investigated areas in modern synthetic chemistry. This statement is clearly supported by the award of the 2001 Nobel Prize in Chemistry to W. S. Knowles, R. Noyori, and K. B. Sharpless for their... 

The asymmetric reduction of carbonyl groups to form enantiopure secondary alcohols is a reaction of fundamental importance in modern synthetic chemistry. The carbonyl group is prochiral centre (if different groups are attached to carbonyl carbon) and can be attacked by hydride from re or si face to generate a racemic product if there are no additional chiral centres in the molecule. 

The inversion of reactivity Umpolung) by the use of masked carbonyls was another achievement of modern synthetic chemistry, yet the direct generation of... 

To study a particular enzyme using the fluorogenic reaction approach, the first challenge is to find a fluorogenic substrate. As discussed above, with modern synthetic chemistry, the availability of suitable substrates is only limited by researchers creativity in designing molecules. 

Aube J (1991) Selectivity, strategy, and efficiency in modern synthetic chemistry. In Trost BM, Fleming I (eds) Comprehensive organic synthesis, vol 1. Pergamon, Oxford, p 822... 

Only small amounts of chemical are needed. Modern synthetic chemistry allows derivative synthesis of analogs and verification of their structure in small batches. If milligram quantities can show potential toxicity why synthesize grams ... 

Up to the 1960s, the treatment of atherosclerosis was only symptomatic. [363] Thus, for example for lowering blood pressure, there was used an extract from the snake-shaped roots of Rauwolfia serpentina, which was already known to the ancient Hindus (Fig. 5.149). [364] In 1952, EmU Schlittler (1906-1979) of the Ciba company isolated reserpine as its hypotensive principle, and determined its constitution. In particular, he also recognised the relationship to the large class of yohimbine alkaloids. The first constitutional total synthesis was achieved in 1956 by R. B. Woodward. [365-367] It counts as one of his most notable contributions to modern synthetic chemistry and formed the basis of industrial processes for the synthesis of this drug. In 1989, Gilbert Stork published a stereospecific total synthesis. [368]... 

The generation of combinatorial libraries plays an important role in modern synthetic chemistry. However, it is advisible to have a look at the possible outcome of these combinatorial experiments in advance to optimize the procedure. 

Organolithium compounds are very reactive as nucleophiles in carbonyl addition reactions even at very low temperatures. They are powerful and effective bases and are widely used in modern synthetic chemistry. As they react rapidly with atmospheric oxygen and moisture, they must be used under an inert atmosphere of Nj or Ar. This... 

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