Basic Concepts Of Retrosynthesis (Part1) 1

reduction (NO2 to NH2), oxidation (CH3 to COOH), diazonium chemistry (NH2 N2+ Ar-X). In aromatic chemistry CCBFR revolve around:With aliphatic acyclic and cyclic systems – the process is not always as straightforward – need to consider a greater array of CCBFR’s and FGI’s.We shall discuss possible synthesis later, but we will concentrate on CCBFR in aliphatic systems.Review and extend CCBFR from 1C1Y, in particular:
Aldol and Claisen condensations
Alkylation of -keto esters (RCHOCH2CO2R’)
Grignard reactions And illustrate their use in synthesis. There are several ways of doing this. We shall consider the following: Note


(Not a typical substitution mechanism!) In the main we will be looking at ionic reactions.In CCBFR the carbonyl group is very importantAlso in CCBFR, organometallic compounds are important.e.g.

RETROSYNTHETIC APPROCH TO ORGANIC SYNTHESIS Prof

65 RETROSYNTHESIS PowerPoint PPTs on …
Photo provided by
Flickr

View Retrosynthesis presentations online, safely and virus-free

This steps are repeated until available starting materials are reached.The retrosynthetic analysis is not a synthesis form of , but an analytical approach based on the desired product.

Learn new and interesting things

6 Forward Synthesis: Free ppton air conditioner Ppton content development director Download ppton IbuprofenR form non-active side Sulfa Antibiotics - Synthesis of Sulfanilamide INTORODUCTIONMany people think of the term chemotherapy as relating to specific modern drugINHIBITORS- PowerPoint PPTPresentation.

View and Download PowerPoint Presentations on SYNTHESIS OF PARACETAMOL PPT. Find PowerPoint Presentations and Slides using the …
Photo provided by
Flickr

Synthesis and Retrosynthesis of Peptidomimetic Inhibitors - Thrombin

Carbonyl compounds having an -hydrogen act as weak (protic) acids and react with a base to yield enolate anions.
Presence of neighbouring carbonyl group increases the acidity of a ketone over an alkane by a factor of 1040! The use of such enolate anions from carbonyl compounds is fundamental to organic synthesis and you will already have met them as intermediates in the Aldol reaction and Claisen condensation.When we have two carbonyl groups adjacent to a methylene group, the acidity of the -H is greatly increased. Because of the acidity of their methylene (CH2) hydrogens, malonic esters, ethylacetoacetate and -dicarbonyl compounds etc are often called active hydrogen compounds.1)They are readily made and cheap2)The anion can be generated quantitatively3)Self condensation does not occur with 1 mole of base – OH is deprotonated4)The site of deprotonation is unambiguous5)The enolate ions formed on deprotonation can be alkylated and acylated offering useful products.Example:Most important use is for preparation of ketones (from -keto esters RCOCH2CO2Et) and of acids from malonic esters (CH2(CO2R)2).Note:

So Retrosynthesis:Note: FGI’s can be carried out on intermediates/products.Note especially:Helps in the synthesis of 1,3 diols.e.g.Usually uses weak base/weak acid as catalyst, (R2NH/HOAc). Any combination of stabilising groups can be used (CN, CO2Et etc).Carbanions derived from active methylene compounds react with-unsaturated compounds by 1,4-(conjugate) addition known as Michael addition.

We have discussed the regioselective reactions of this active methylene carbon (C-2) in ethylacetoacetate. Can regiospecifically trap C-4 via the dianion.Carbonyl Addition and Carbonyl Substitution – Aldol and Claisen Reactions.Usually self-condensations, these reactions combine nucleophilic attack and -substitution as the first step.Note the Aldol condensation can also be performed with acid catalysis in which dehydration usually follows (enol form is involved – mechanism p 773). NB dehydration drives the reaction when the equilibrium is unfavourable.

Note: the only difference between the Aldol and Claisen reaction is the fate of the tetrahedral intermediate – Claisen expels alkoxide, Aldol alkoxide is protonated.These are not very useful generally as there are four potential products. However, they can be useful if one component has no -H.Mixed AldolMixed Claisen CondensationsOnly successful when one of the ester components has no -H e.g.

Retrosynthetic analysis is a technique for solving problems in the ..

via Grignard reagents) - suggests alternative synthesis to Friedel Crafts.In planning a synthetic strategy, apart from devising a means of constructing the carbon skeleton with the required functionality as above, there are other subtle factors, which we must address.(Good summary p169 – 172, 259 – 260, 354 – 359)We will illustrate this approach with examples, starting with synthesis of benzene derivatives. Starting point is usually fairly obvious – simple benzene derivatives or perhaps benzene itself.Reactions are usually straightforward (SEAr) and you will have met most of them before. Synthesis is simplified because the nature of the starting materials is usually clear. Thus, most reactions correspond to the following disconnection:1st decision – which bond to disconnect first!However, we can carry out monobromination on the N-acyl derivative of the amine:then we can remove the protecting group (HO-/H2O) to give the required product.So formally: Is there an alternative route? Try a different FGI!

An introduction to retrosynthetic analysis - YouTube

labelled compounds).d)For the intellectual challenge – new problems demand new solutions and can lead to the development of NEW CHEMISTRY, reagents etc.When faced with the challenge of preparing a specific organic compound ho do we go about it?This is the art of synthesis!e.g.

retrosynthesis organic chemistry ppt - Universo Online

PhCO2Et OR HCOOEt.When certain dicarbonyl compounds are treated with base intramolecular Aldol reactions can occur. Similarly diesters can undergo intramolecular Claisen Condensations (this reactions is known as the Dieckmann cyclisation).

The intramolecular Aldol condensation forms the basis of a very useful method for making rings – The Robinson Annulation Reaction:Reaction works best with 1,6 or 1,7 diesters to give 5 or 6 membered rings.

Alkylation is regiospecific.Very useful method for alkene synthesis as the position of the double bond is known.