Organic synthesis retrosynthetic analysis

Organic synthesis is stressed throughout this book, with progressive discussions of the process involved in developing a synthesis. Retrosynthetic analysis is emphasized, and the student learns to work backward from the target compound and forward from the starting materials to find a common intermediate. 

Introduction to Organic Chemical Synthesis Retrosynthetic Analysis... 

Scheme 1 outlines the retrosynthetic analysis of the Woodward-Eschenmoser A-B variant of the vitamin B12 (1) synthesis. The analysis begins with cobyric acid (4) because it was demonstrated in 1960 that this compound can be smoothly converted to vitamin B12.5 In two exploratory corrin model syntheses to both approaches to the synthesis of cobyric acid,6 the ability of secocorrinoid structures (e. g. 5) to bind metal atoms was found to be central to the success of the macrocyclization reaction to give intact corrinoid structures. In the Woodward-Eschenmoser synthesis of cobyric acid, the cobalt atom situated in the center of intermediate 5 organizes the structure of the secocorrin, and promotes the cyclization... 

When planning an organic synthesis in this way, we cannot apply an individual transform only because the corresponding retron is present in the target molecule. It is necessary to carry on an accurate analysis with a perspective (outlook) of several retrosynthetic steps, in order to see if a particularly adequate sequence of transforms exists. 

In Part V we show you how to pull all the previous information together and use it to develop strategies for designing synthesis reactions. We talk about both one-step and multistep synthesis as well as retrosynthetic analysis. Then we tackle the dreaded organic roadmaps. (We all wish we had an organic chemistry GPS here.)... 

In your first semester of organic chemistry you studied regiochemistry and retrosynthesis. The type of director (o-p or m) is an important aspect of this regiochemistry that you need to consider in any synthesis or retrosynthetic analysis problem. 

In many cases, a desired compound cannot be synthesized directly from readily available materials. In these cases, a multistep synthesis must be performed. Figure 13-47 illustrates a multistep synthesis. (A similar type of problem appears on many Organic Chemistry II exams they re retrosynthetic analysis problems.)... 

The principal exponent of the non-computerised approach to retrosynthetic analysis in organic synthesis, and which finds its origin in the early work of E. J. Corey, is S. Warren.5c d A useful shorter account is to be found in the writings of J. Fuhrhop and G. Penzlin.5 The non-computerised retrosynthetic analysis has also been termed the synthon approach, a term which was first introduced and defined by E. J. Corey.15... 

Chapter 8 begins the treatment of organic reactions with a discussion of nucleophilic substitution reactions. Elimination reactions are treated separately in Chapter 9 to make each chapter more manageable. Chapter 10 discusses synthetic uses of substitution and elimination reactions and introduces retrosynthetic analysis. Although this chapter contains many reactions, students have learned to identify the electrophile, leaving group, and nucleophile or base from Chapters 8 and 9. so they do not have to rely as much on memorization. Chapter 11 covers electrophilic additions to alkenes and alkynes. The behavior of carbocations, presented in Chapter 8, is very useful here. An additional section on synthesis has been added to this chapter as well. 

This chapter is meant to give you just the basic ideas of retrosynthetic analysis. They are important because they reinforce the concept that the combination of electrophile and nucleophile is the basis for the understanding of organic reactions. Synthesis and reactions are two sides of the same coin. From now on we shall use the methods introduced in this chapter when we think that they will help you to develop your understanding. 

Chapter 1 is devoted to exploring strategies involved in organic synthesis. It seeks to explain concepts like retrosynthetic analysis, atom economy, umpolung approach, click chemistry and asymmetric synthesis. On the basis of interesting and relevant examples, protection and deprotection of different functional groups are explained and the most probable mechanism is also mentioned for important reactions. 

Organic synthesis has undergone the transformation from a purely heuristic discipline into a solid branch of science with its own logistics and technology based on the principles of retrosynthetic analysis. An essential part of retro-synthetic analysis involves the sequential disconnection of the target molecule... 

Problem 11.23 Use retrosynthetic analysis to show how 3-hexyne can be prepared from acetylene and any other organic and inorganic compounds. Then draw the synthesis in the synthetic direction, showing all needed reagents. 

To use the Heck reaction in synthesis, you must determine what alkene and what organic halide are needed to prepare a given compound. To work backwards, locate the double bond with the aryl, COOR, or CN substituent, and break the molecule into two components at the end of the C = C not bonded to one of these substituents. Sample Problem 26.3 illustrates this retrosynthetic analysis. 

Synthesis Synthesis, one of the most difficult topics for a beginning organic student to master, is introduced in small doses beginning in Chapter 7, and augmented with a detailed discussion of retrosynthetic analysis in Chapter 11. In later chapters, special attention is given to the retrosynthetic analysis of compounds prepared by carbon-carbon bondforming reactions (for example. Sections 20.11 and 21.IOC). 

The intensity of activity in the field of thiazole and benzothiazole research reflects the importance of these heterocycles in organic and biological chemistry. There has therefore been a large volume of synthesis literature produced since 1995. The following section has been ordered according to the fragments generated by retrosynthetic analysis, which are shown in Scheme 53. 

The following discussion on retrosynthetic analysis covers topics similar to those in Warren s Organic Synthesis The Disconnection Approach and Willis and Will s Organic Synthesis. For an advanced treatment of the subject matter, see Corey and Cheng s The Logic of Chemical Synthesis. 

---