Retrosynthetic analysis retrosynthesis

Example 6.1 Recognition of TM 6.1 as an anilide of iV-alkylated and Af-acylated a-amino acid valine suggests obvious retrosynthetic analysis. Retrosynthesis leads over three consecutive disconnections of C-N bonds to valine and the three additional building blocks (Scheme 6.4). 

Synthesis and Retrosynthetic Analysis Retrosynthesis of 2-Pentanone Using Reactions of Carbonyl Compounds... 

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. 

The active development, support, and distribution of WODCA was stopped in 2005. The distributor. Molecular Networks — a spin-off of Gasteiger s research team — is currently developing a Web-based expert system called Retrosynthesis Browser (RSB) for retrosynthetic analysis of a given target compound. RSB scans reaction databases to suggest new synthetic routes and simultaneously searches in catalogs of available starting materials for the proposed precursors. 

Figure 10.4. LHASA transform and retrosynthetic analysis. (a) Display of LHASA transform, (b) Retrosynthesis of Target 3 to acetophenone, (c) Part of the tree from the retrosynthetic analysis of target, (d) Retrosynthetic removal of the hydroxymethyl group from target 3 by a route involving an organometallic addition transform.

For the retrosynthesis of indole (see Fig. 5.8), two routes (I/II) are proposed, as for pyrrole (see p 94). Route I suggests o-aminobenzyl ketone 1 or 6>-alkyl-A -acylaniline 2 as starting material on the basis of operations a - c. Their retroanalysis (d,e) in turn leads to 2-alkylaniline 5 and carboxylic acid derivative 6. Construction of the indole system should thus occur by N- or C-acylation of 5 (utilizing the o-nitrotoluene derivative 4) followed by cyclodehydration of 1/2. The alternative route n, based on retrosynthetic analysis g-i, leads to aniline via the a-(A -phenylamino)ketones 3 and to a-halo ketones 7 as possible precursors for the indole synthesis. 

The synthesis of 2//-pyran-2-one follows the route indicated by the retrosynthesis (see Fig. 6.4). According to a and b, the retrosynthetic analysis involves the O/C-2 bond and suggests the... 

Synthetic planning starts with the product, which is fixed and unchangeable, and works backwards towards the starting materials. This process is called retrosynthesis, and the art of planning the synthesis of a target molecule is called retrosynthetic analysis. The aim of this chapter is to introduce you to the principles of retrosynthetic analysis once you have read and understood it you will be well on the way to designing your own organic syntheses. 

The first problem will prepare 4-bromoaniline (168) from benzene. Syntheses that transform one aromatic compound into another aromatic compound, such as this one, do not lend themselves to the retrosynthetic analysis approach presented in Chapter 25. Most of these syntheses involve functional group transformations. For the sake of continuity, a retrosynthesis is shown in which the amino group is removed to generate bromobenzene, which is obtained directly from benzene. The NH2 unit probably comes from reduction of a nitro group (Section 21.6.2), so the first precursor is 4-bromonitrobenzene (59) and disconnection of the C-N bond leads to the preparation of 59 by reaction of bromobenzene (35) with nitric acid/sulfuric acid. Bromobenzene is prepared directly from benzene as shown in the illustration. 

Use retrosynthetic analysis to devise a synthesis of m-chloroethylbenzene from benzene. Convert your retrosynthesis to a synthesis and show the necessary reagents for each step. Hint A Clemmensen or Wolff-Kishner reduction is necessary.)... 

Now we start with the study of retrosynthesis by the problem-solving approach. This approach has characteristics of seminar work promoting knowledge of organic synthesis by retrosynthetic consideration of selected target molecules. They are either of commercial or scientific interest, and their retrosynthetic analysis has a certain didactic value. In the next few examples we approach the disconnection of compounds with one functional group, represented by carbinols, and tertiary alcohols. 

While presenting principles of retrosynthetic analysis, we do not devote attention to the formation of stereoisomers. There is a good reason for departure into the third dimension after the introductory chapters where the stereochemical aspects of retrosynthesis and the stereoselectivity of the corresponding synthetic steps are not considered. 

On first sight, it is diflftcult to imagine rc/ro-Mannich disconnection as the key step in the retrosynthesis of TM 4.13. Starting the retrosynthetic analysis with the disconnection of the C=C bond in cyclic enone we arrive at a 1,5-dicarbonyl pattern in TM 4.13a (Scheme 4.41). Now two possible refro-Michael disconnections. 

The retrosynthetic analysis of TM 8.3 presented in Scheme 8.8 involves a proposal for the retrosynthesis of 3-aminopyridine TM 8.3a. 

The first synthesis of 1 was completed according to the presented retrosynthesis [28]. It deviates somewhat from the retrosynthetic analysis in some details, as presented in Scheme 9.19. Additional steps to racemic a-lycorane TM 9.4 are included in the scheme. 

Nowadays retrosynthetic packages, workshops and retrosynthesis competitions are being developed by collaborations of industry and academy. The authors expect this book to contribute to this trend and bridge retrosynthetic analysis and asymmetric synthesis of chiral target molecules in the optically pure form. 

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