Overview of Synthesis Strategies

Synthesis is actually the reverse of predicting products. In synthesis, you have the product of a reaction and you must predict the reaction sequence necessary to form the product. While you may have hints as to the identity of the starting material, in most cases you need to predict the starting material, the reactants, and possibly the reaction conditions. You encounter two general types of synthesis questions — one-step synthesis and multistep synthesis. As the name implies, a one-step synthesis problem requires one simple answer. A multistep synthesis involves more than one reaction, and more than one answer may be correct. On an organic chemistry exam, one-step synthesis questions usually focus on the most recent reactions you have studied, whereas multistep synthesis questions usually involve a recent reaction in one step and one or more other reactions from any point in Organic Chemistry 1 or 11 in other steps. 

When predicting products you should ask yourself three basic questions, and the same questions are also important when considering synthesis problems  

1/ What is the regiochemistry of the reaction (the chemical environment of the reactive site on this molecule for this pcirticular reaction)  

However, you need to apply these questions in a different way for synthesis problems than for predicting problems. 

If the question starts with a ketone, what do you do When predicting products, you must consider every reaction you know that begins with a ketone. When doing a synthesis problem, you must consider every reaction that produces a ketone. 

On an organic chemistry exam, if the instructor takes time to draw the specific stereochemistry of a molecule, it s a hint that you should carefully consider the stereochemistry of any reactions you use. 

To do any synthesis problem, you must know your reactions backwards and forwards. This takes time and effort. To learn them thoroughly, you need to practice over and over. During an exam, you don t have time to work out every possibility, so you must know the reactions. 

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A short overview of synthetic strategies that are currently used in combinatorial chemistry is important to get a better understanding of how to characterize a combinatorial library in the most efficient way. Figure 10.3 presents different strategies for synthesis of combinatorial libraries on an example of a library with three points of randomization (X, Y, Z), three building blocks in each randomization (XI, X2, X3, Yl, Y2, etc., correspondingly), and total complexity of 27 compounds. 

Abstract This chapter provides an overview of emerging strategies for the selective introduction of functionality at oxindole C3. Specific emphasis has been devoted toward asymmetric methods for the introduction of C3 quaternary centers and spirocyclic ring systems. The chapter has been divided into two sections oti general methodology for the stereoselective synthesis of oxindoles and spirooxin-doles, respectively. A third section is devoted toward efforts in natural product total synthesis involving oxindole or spirocyclic variants as targets or key intermediates. 

Oligo- and polyarylenevinylenes are available via a variety of different, often very powerful, synthetic approaches the next section will give a brief overview of the most common strategies to generate this type of structures. In this context, emphasis will be placed on the synthesis of structurally defined and well-characterized materials. 

The synthesis of carbonyl colorants uses a wide diversity of chemical methods, in which each individual product essentially has its own characteristic route. This is in complete contrast to the synthesis of azo dyes and pigments (Chapter 3) where a common reaction sequence is universally used. The subject is too vast to attempt to be comprehensive in a text of this type. The following section, therefore, presents an overview of some of the fundamental synthetic strategies which may be used to prepare some of the more important types of carbonyl colorants. 

In a continuous effort to circumvent the problem of poor solubility and tune the steric effects and electronic features of Pcs, several effective strategies have been developed. As a result, in recent years many neutral Pcs containing substituents at peripheral a or p positions, or in the axial direction, as well as ionic and sandwich-type Pcs have been synthesized and their single-crystal structures resolved by X-ray diffraction analysis [15-24], It therefore appears necessary to give a relatively comprehensive overview of the new progress in Pc chemistry. In this chapter, we summarize recent research results on the synthesis, crystal structures, and various physical properties of monomeric Pc compounds. 

In this review I have attempted to give a comprehensive overview of the published work on nanoporous materials prepared from ordered block copolymers. Given the numerous successful demonstrations of the block copolymer strategy in the design, synthesis, and applications of nanoporous materials, this methodology holds a great deal of promise for the bottom-up en-... 

A key aspect of any synthesis strategy on a polymeric support is the linkage element, which acts as a tether to the polymeric support. Ideally, the linker should be stable to all reaction conditions used in a synthesis sequence and should be cleaved quantitatively under conditions that do not degrade the desired target molecule [6]. In this overview the different kinds of linkers and the synthetic transformations that can be used on polymeric supports will be presented. At the end, synthetic strategies for the synthesis of heterocycles and natural products will be mentioned. 

An overview of the work in this field is presented in Table 11.5, see also recent reviews (Luisi et al, 2006). This table also contains references to the work mentioned earlier, such as poly(A) synthesis from ADP the PCR reaction in liposomes the RNA synthesis by QP replicase, as well as the expression of poly(Phe) by an entrapped ribosomal system. This work is preliminary to protein expression in liposomes. Going from here to the protein synthesis, it may be useful to compare the different strategies for the expression of GFP. 

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