Multistep synthesis retrosynthetic analysis

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 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.)... 

Considering multistep synthesis for more complicated problems Solving sample problems with retrosynthetic and synthetic analysis... 

Retrosynthetic analysis is a method for tackling synthesis problems, especially multistep synthesis problems. The application of this technique involves working the problem backwards, starting at the final product and ending up with the initial reactants. 

When applying retrosynthetic analysis to a multistep synthesis problem, you must work backwards. If you become lost, as a last resort you may want to look at the forward reactions. However, the forward process often goes off on a tangent or leads to a cul-de-sac. 

When you see a synthesis problem for the first time, you are not expected to immediately know the answer. I cannot stress this enough. It is so common for students to get overly anxious when they see synthesis problems that they cannot solve. Get used to it. This is the way it is supposed to be. Going back to our chess analogy, you don t need to make a move as soon as it is your turn. You are allowed to think about it first. In fact, you are supposed to think about it first. So, how do you begin thinking about a multistep synthesis problem w here you do not immediately see the solution The most powerful technique is called retrosynthetic analysis. This means that you analyze the problem backward. Let s see how this works w ith an example ... 

Q Use retrosynthetic analysis to solve multistep synthesis problems with alkenes as reagents, intermediates, or products. 

ILLUSTRATING A MULTISTEP SYNTHESIS Show how phenylacetylene (CeH5C = CH) could be synthesized from ethylbenzene (phenylethane). Begin by writing a retrosynthetic analysis, and then write reactions needed for the synthesis. 

Students are introduced to synthetic chemistry and retrosynthetic analysis early in the book (Chapters 6 and 7, respectively), so they can start designing multistep syntheses early in the course. Nine special sections on synthesis design, each with a different focus, are introduced at appropriate intervals. There is a new tutorial on synthesis and retrosynthetic analysis that includes some examples of complicated multistep syntheses from the literature. 

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