Retrosynthetic analysis is a technique used to plan organic syntheses by working backwards from the target molecule. It involves mentally deconstructing the target molecule through sequential disconnections and functional group transformations until commercially available starting materials are reached. Each disconnection produces synthons, which are idealized fragments that represent possible reaction precursors. Common types of disconnections include C-X, C-C, and carbonyl bonds. The goal of retrosynthesis is to simplify the target structure and design multiple possible synthesis routes leading from simple starting materials to the target. It helps chemists discover efficient syntheses by considering the reactivity, selectivity, and availability of materials at each step.
Retrosynthetic analysis, definition, importance, disconnection approach, one group two group disconnection logical and illogical disconnection approach compounds containing two nitrogen atom retrosynthetic analysis of camphor, cartisone, reserpine
An approach for designing organic synthesis which involves breaking down of target molecule into available starting material by imaginary breaking of bonds (disconnection) and/or by functional group interconversion is known as disconnection approach or retrosynthesis or synthesis backward.
The C-X disconnection approach is mainly applicable to a carbon chain attached to any of the heteroatoms like O, N, or S. Here, a bond joins the heteroatom (X) to the rest of the molecule like a C-O, C-N, or C-S group. This point is good point to initiate a disconnection. This is called a ‘One-group’ C-X disconnection as one would need to identify only one functional group like ester, ether, amide etc. to make the disconnection.
How to choose a disconnection?
These are the few general strategy which are important points introduced which apply to the whole of synthetic design rather than one particular area. The main choice is between the various disconnection, even such a simple disconnection as the following alcohol can be disconnected.
We want to get back to simple starting materials and we shall do if we disconnect the bond which are:
Towards the middle of the molecule thereby breaking into two reasonably equal halves rather than chopping off one or two carbon atoms from the end and,
At a branch as this is more likely to give straight chain fragments and these are more likely to be available.
Disconnections very often take place immediately adjacent to, or very close to functional groups in the target molecule. This is pretty much inevitable, given that functionality almost invariably arises from the forward reaction.
A simple example is the weedkiller propanil used on rice fields. Amide disconnection gives amine obviously made from o-dichlorobenzene by nitration and reduction. All positions around the ring in o-dichlorobenzene are about the same electronically but steric hindrance will lead to dichloronitrobenzene being the major product
This compound was needed for some research into the mechanisms of rearrangements. We can disconnect on either side of the ether oxygen atom, but (b) is much better because (a) does not correspond to a reliable reaction: it might be hard to control selective alkylation of the primary hydroxyl group in the presence of the secondary one.
The disconnections we have made so far have all been of C–O, C–N, or C–S bonds, but, of course, the most important reactions in organic synthesis are those that form C–C bonds. We can analyze C–C disconnections in much the same way as we’ve analyzed C–X disconnections.
The Zeneca drug propranolol is a beta-blocker that reduces blood pressure and is one of the top drugs worldwide. It has two 1,2-relationships in its structure but it is best to disconnect the more reactive amine group first.
Arildone is a drug that prevents polio and herpes simplex viruses from ‘unwrapping’ their DNA, and renders them harmless.
Presented by Shikha Popali and Harshpal singh Wahi students from Gurunanak college of pharmacy, Nagpur in Department of pharmaceutical Chemistry. The explained topic is seful for every chemistry student and for others too
For B Pharmacy and M Pharmacy Students
Subscribe to the YouTube Channel
#Professor_Beubenz
https://www.youtube.com/channel/UC84jGf2iRN5VjwnQqi6qmXg?view_as=subscriber
Retrosynthetic analysis, definition, importance, disconnection approach, one group two group disconnection logical and illogical disconnection approach compounds containing two nitrogen atom retrosynthetic analysis of camphor, cartisone, reserpine
An approach for designing organic synthesis which involves breaking down of target molecule into available starting material by imaginary breaking of bonds (disconnection) and/or by functional group interconversion is known as disconnection approach or retrosynthesis or synthesis backward.
The C-X disconnection approach is mainly applicable to a carbon chain attached to any of the heteroatoms like O, N, or S. Here, a bond joins the heteroatom (X) to the rest of the molecule like a C-O, C-N, or C-S group. This point is good point to initiate a disconnection. This is called a ‘One-group’ C-X disconnection as one would need to identify only one functional group like ester, ether, amide etc. to make the disconnection.
How to choose a disconnection?
These are the few general strategy which are important points introduced which apply to the whole of synthetic design rather than one particular area. The main choice is between the various disconnection, even such a simple disconnection as the following alcohol can be disconnected.
We want to get back to simple starting materials and we shall do if we disconnect the bond which are:
Towards the middle of the molecule thereby breaking into two reasonably equal halves rather than chopping off one or two carbon atoms from the end and,
At a branch as this is more likely to give straight chain fragments and these are more likely to be available.
Disconnections very often take place immediately adjacent to, or very close to functional groups in the target molecule. This is pretty much inevitable, given that functionality almost invariably arises from the forward reaction.
A simple example is the weedkiller propanil used on rice fields. Amide disconnection gives amine obviously made from o-dichlorobenzene by nitration and reduction. All positions around the ring in o-dichlorobenzene are about the same electronically but steric hindrance will lead to dichloronitrobenzene being the major product
This compound was needed for some research into the mechanisms of rearrangements. We can disconnect on either side of the ether oxygen atom, but (b) is much better because (a) does not correspond to a reliable reaction: it might be hard to control selective alkylation of the primary hydroxyl group in the presence of the secondary one.
The disconnections we have made so far have all been of C–O, C–N, or C–S bonds, but, of course, the most important reactions in organic synthesis are those that form C–C bonds. We can analyze C–C disconnections in much the same way as we’ve analyzed C–X disconnections.
The Zeneca drug propranolol is a beta-blocker that reduces blood pressure and is one of the top drugs worldwide. It has two 1,2-relationships in its structure but it is best to disconnect the more reactive amine group first.
Arildone is a drug that prevents polio and herpes simplex viruses from ‘unwrapping’ their DNA, and renders them harmless.
Presented by Shikha Popali and Harshpal singh Wahi students from Gurunanak college of pharmacy, Nagpur in Department of pharmaceutical Chemistry. The explained topic is seful for every chemistry student and for others too
For B Pharmacy and M Pharmacy Students
Subscribe to the YouTube Channel
#Professor_Beubenz
https://www.youtube.com/channel/UC84jGf2iRN5VjwnQqi6qmXg?view_as=subscriber
It is an intramolecular rearrangement reaction in which the 1,2-migration of silyl group from carbon to oxygen under basic conditions.It involves the formation of a pentacoordinate siliconintermediate.Discovered by Adrian Gibbs Brook in 1958.
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
Contents includes at least three strategies of synthesis for each of three, four, five and six membered heterocylic ring with one or two heteroatoms. One mechanism described out of the three strategies. Few name reactions are described and the other are simple synthetic methods. This presentation was prepared for the partial fulfillment of Master of Pharmacy. The content was taken from the various books, mentioned in slide with the title of references.
Asymmetric synthesis FOR BSc, MSc, Bpharm, M,pharmShikha Popali
ASYMETRIC SYNTHESIS PRESENTED BY SHIKHA AND HARSHPAL SINGH IN EASY WAY WHICH IS EASILY UNDERSTANDABLE AND GIVES A DETAIL ACCOUNT USEFUL FOR EVERY CHEMISTRY PERSON
This is an experiment. It is NOT a presentation. It is meant to be an interactive pdf for students to work through/revise from at their own pace. For these features to operate I guess it needs to be downloaded first.
It is based on 123.312 lectures on retrosynthesis or the design of chemical syntheses.
When there are two functional groups of unequal reactivity within a molecule, the more reactive group can be made to react alone, but it may not be possible to react the less reactive functional group selectively.
A group the use of which makes possible to react a less reactive functional group selectively in presence of a more reactive group is known as protecting group.
A protecting group blocks the reactivity of a functional group by converting it into a different group which is inert to the conditions of some reaction(s) that is to be carried out as part of a synthetic route
It is an intramolecular rearrangement reaction in which the 1,2-migration of silyl group from carbon to oxygen under basic conditions.It involves the formation of a pentacoordinate siliconintermediate.Discovered by Adrian Gibbs Brook in 1958.
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
Organic Synthesis:
The Disconnection Approach
One Group C-C Disconnection of Alcohol and Alkene
Contents includes at least three strategies of synthesis for each of three, four, five and six membered heterocylic ring with one or two heteroatoms. One mechanism described out of the three strategies. Few name reactions are described and the other are simple synthetic methods. This presentation was prepared for the partial fulfillment of Master of Pharmacy. The content was taken from the various books, mentioned in slide with the title of references.
Asymmetric synthesis FOR BSc, MSc, Bpharm, M,pharmShikha Popali
ASYMETRIC SYNTHESIS PRESENTED BY SHIKHA AND HARSHPAL SINGH IN EASY WAY WHICH IS EASILY UNDERSTANDABLE AND GIVES A DETAIL ACCOUNT USEFUL FOR EVERY CHEMISTRY PERSON
This is an experiment. It is NOT a presentation. It is meant to be an interactive pdf for students to work through/revise from at their own pace. For these features to operate I guess it needs to be downloaded first.
It is based on 123.312 lectures on retrosynthesis or the design of chemical syntheses.
When there are two functional groups of unequal reactivity within a molecule, the more reactive group can be made to react alone, but it may not be possible to react the less reactive functional group selectively.
A group the use of which makes possible to react a less reactive functional group selectively in presence of a more reactive group is known as protecting group.
A protecting group blocks the reactivity of a functional group by converting it into a different group which is inert to the conditions of some reaction(s) that is to be carried out as part of a synthetic route
Organic Reaction Mechanism : This topic is very-very important for CSIR-NET, GATE, IIT-JAM and other Competitive exams for Chemistry and Chemical Sciences.
Cycloaddition reactions: combination of two words "cyclo" and "addition", which means addition of two molecules to form a new ring system.
Reterocycloaddition reactions : reverse of cycloaddition reactions is known as reterocycloaddition reactions
Types of cycloaddition reactions
Mechanism of cycloaddition reactions
Suprafacial and antarafacial interactions
Woodward-Hoffmann rule for cycloaddition reactions
Examples and applications of cycloaddition reactions
The Art Pastor's Guide to Sabbath | Steve ThomasonSteve Thomason
What is the purpose of the Sabbath Law in the Torah. It is interesting to compare how the context of the law shifts from Exodus to Deuteronomy. Who gets to rest, and why?
Model Attribute Check Company Auto PropertyCeline George
In Odoo, the multi-company feature allows you to manage multiple companies within a single Odoo database instance. Each company can have its own configurations while still sharing common resources such as products, customers, and suppliers.
The French Revolution, which began in 1789, was a period of radical social and political upheaval in France. It marked the decline of absolute monarchies, the rise of secular and democratic republics, and the eventual rise of Napoleon Bonaparte. This revolutionary period is crucial in understanding the transition from feudalism to modernity in Europe.
For more information, visit-www.vavaclasses.com
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Students, digital devices and success - Andreas Schleicher - 27 May 2024..pptxEduSkills OECD
Andreas Schleicher presents at the OECD webinar ‘Digital devices in schools: detrimental distraction or secret to success?’ on 27 May 2024. The presentation was based on findings from PISA 2022 results and the webinar helped launch the PISA in Focus ‘Managing screen time: How to protect and equip students against distraction’ https://www.oecd-ilibrary.org/education/managing-screen-time_7c225af4-en and the OECD Education Policy Perspective ‘Students, digital devices and success’ can be found here - https://oe.cd/il/5yV
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
Synthetic Fiber Construction in lab .pptxPavel ( NSTU)
Synthetic fiber production is a fascinating and complex field that blends chemistry, engineering, and environmental science. By understanding these aspects, students can gain a comprehensive view of synthetic fiber production, its impact on society and the environment, and the potential for future innovations. Synthetic fibers play a crucial role in modern society, impacting various aspects of daily life, industry, and the environment. ynthetic fibers are integral to modern life, offering a range of benefits from cost-effectiveness and versatility to innovative applications and performance characteristics. While they pose environmental challenges, ongoing research and development aim to create more sustainable and eco-friendly alternatives. Understanding the importance of synthetic fibers helps in appreciating their role in the economy, industry, and daily life, while also emphasizing the need for sustainable practices and innovation.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
2. DEFINITION[ 2 ]
• Retrosynthetic (or antithetic) analysis is a problem solving technique for
transforming the structure of a synthetic target molecule (TGT) to a sequence of
progressively simpler structures along a pathway which ultimately leads to simple or
commercially available starting materials for a chemical synthesis.
• The transformation of a molecule to a synthetic precursor is accomplished by the
application of a transform, the exact reverse of a synthetic reaction, to a TGT.
• Each structure derived antithetically from a target the itself becomes a TGT for a
further analysis. Repetition of this process eventually produces a tree of
intermediates having chemical structural as nodes and pathways from bottom to top
corresponding to possible synthetic routes to the TGT.
4. • RETROSYNTHETIC ANALYSIS or
RETROSYNTHESIS “The process of WORKING
BACKWARD from the TM in order to devise suitable
synthetic route”
OR
“The process of mentally breaking down a molecule into a
starting material”
OR
“It is a problem solving technique for transforming the
structure of a synthetic target molecule (TM) to a sequence
of progressively simpler structures along a pathway which
ultimately leads to simple or commercially available starting
materials for a chemical synthesis.”[2]
5. ARROW NOTATION [2]
• 1.Simple reaction arrow “ reacts to give”
• 2. Delocalisation arrow “two different
ways to draw the same delocalised structures”
• 3.Equilibrium arrow ⇌ “two structures are
interconverting”
• 4. Curved arrow “motion of two
electrons” ( Single Headed)
• 5. Fish-hook arrow “motion of one electron”
• 6. Curved arrow ( Double Headed)
6.
7. TERMINOLOGY[ 2 ]
• Target molecule (TM): the molecule to be synthesized
• Retrosynthetic analysis or retrosynthesis: the process of mentally breaking down a
molecule into a starting material
• Disconnection: an imaginary bond cleavage corresponding to a reverse of a real reaction
• Functional Group Interconversion (FGI): the process of converting one functional
group into another by substitution, addition, elimination, reduction, or oxidation
• Transform: the exact reverse of a synthetic reaction
• Retron: structural subunit on the target that enables a transform to operate
• Synthon: idealized fragment resulting from a disconnection, which is related to possible
synthetic operations
• Umpolung: reversal of normal polarization of a molecule or synthon
• Reagent: a real chemical compound used as the equivalent of a synthon
• Synthesis tree: set of all the possible disconnections and synthons leading from the target
to the starting materials of a synthesis
8. • RETROSYNTHETIC ANALYSIS CAN BE DONE
BY TWO METHODS:
a) Disconnection
b) Functional Group Interconversion (FGI)
• a) Disconnection It is a paper operation involving
an imagined cleavage of a bond. As a result of
disconnection usually negative ion and positive ion
are formed which are called ‘SYNTHONS’
Disconnection is shown by a wavy line like ~ or
VVVVVVVV
9. • b) Functional Group Interconversion (FGI) :
The process of writing one functional group for another
to help synthetic planning is known as FGI. FGI can be
done by,
Addition
Substitution
Elimination
Oxidation/Reduction
Free Radical Reaction
10. DISCONNECTIONS[ 4 ]
• C-X disconnections
If we need to make a C-X bond (where X is a heteroatom),a
simple disconnections reveals a carbocationic synthon. We
choose this polarity because X is almost invariably more
electronegative than carbon. The C-X bond could exist in
many different chemical environments which means there will
be a correspondingly wide range of carbocationic synthons
and synthetic equivalents.
11. • The second of these examples is hugely important: these are acylation reactions
• The third of the C-X disconnections is an example of a two-group
disconnection(like the Diels-Alder example)
12. C-C DISCONNECTIONS
• Alcohols-
Alcohols are prime example of the need to disconnect right
next to the hydroxyl functional group. A carbanion synthon
and an α-hydroxyalkyl cation synthon. The synthetic
equivalent of a carbanion synthon is almost invariably an
organometallic compound.
13. Adding an organometallic compound to a
carbonyl compound generates a new
stereocentre and its non-trivial to control which
enantiomer of the product is formed. If we
disconnect one bond further away from the
alcohol in the target we generate a ß-
hydroxyalkyl cation synthon whose synthetic
equivalent we ve seen in an epoxide.Epoxides
are already chiral, so we have a single
enantiomer of the epoxide, we form a single
enantiomer of the product alcohol.
14. • Carbonyl Compounds
By direct analogy with the disconnection of alcohols,simple carbonyl
compounds disconnect back to acyl cation synthons and carbanionic
synthons.
15. • Synthons[3]: Synthons are the imaginary fragments obtained by
disconnection. The concept of bond polarity with the fragments
is of prime importance during disconnection. Synthons are not
real compounds but are idealized ionic or neutral fragments,
and they are not reagents.
• The following reaction shows a concerted cycloaddition
reaction, where the synthons are neutral fragments.
16. • The symbol signifies a reverse synthetic step and is
called a transform. The main transforms are
disconnections, or cleavage of C-C bonds, and
functional group interconversions (FGI)
• Retrosynthetic analysis involves the disassembly of a
TM into available starting materials by sequential
disconnections and functional group
interconversions(FGI).[4]
• Synthons are fragments resulting from disconnection
of carbon-carbon bonds of the TM. The actual
substrates used for the forward synthesis are the
synthetic equivalents (SE)
17. STEREOSPECIFICITY AND
STEREOSELECTIVITY
• Diels-Alder reaction occurs in one step so that neither dienes nor
dienophile has time to rotate and stereochemistry of each remains
preserved in the product.
• Thus, with respect to the dienophile and the diene the addition is
stereospecific and almost always.
• The Diels- Alder reaction is stereospecific. The cis dienophiles give the
cis product and trans dienophile give trans product.
18. APPLICATION[ 3 ]
• Retrosynthetic analysis is a technique for solving problems in
the planning of organic synthesis. This is achieved by
transforming a target molecule into simpler precursor structures
regardless of any potential reactivity/interaction with reagents.
• Each precursor material is examined using the same method.
This procedure is repeated until simple or commercially available
structures are reached. These simpler/commercially available
compounds can be used to form a synthesis of the target molecule
• The power of retrosynthetic analysis becomes evident in the
design of a synthesis. The goal of retrosynthetic analysis is
structural simplification. Often, a synthesis will have more than
one possible synthetic route.
19. • Retrosynthesis is well suited for discovering
different synthetic routes and comparing them in a
logical and straightforward fashion A database may
be consulted at each stage of the analysis, to
determine whether a component already exists in
the literature. In that case, no further exploration of
that compound would be required. If that
compound exists, it can be a jumping point for
further steps developed to reach a synthesis.
20. GUIDELINES FOR CHOOSING
DISCONNECTIONS[ 2 ]
• 1.Synthesis backwards: The process of breaking
down a target molecule into available starting
materials by disconnection or FGI
• 2.Retrosynthetic arrow: A double line arrow used
to indicate the reverse of a synthetic reaction.
• 3.Synthon: An idealized fragment (usually a cation
or anion) resulting from a disconnection.
• 4. Synthetic equivalent: A real chemical
• 5.Disconnections must correspond to the reverse of
real and workable reactions.
21. • 6. For compounds consisting of two parts joined by a
hetroatom, disconnect next to the hetro atom
• 7. Consider alternate disconnections and choose routes that
avoid chemoselectivity problems. This can often be done by
disconnecting more reactive groups first.
• 8. Evaluate all the possible advantages and disadvantages of
each path- determine the most efficient route for synthesis.
• 9. Evaluation is based on specific restrictions and limitation of
reactions in the sequence, the availability of materials and
other factors.
• 10.In reality, it may be necessary to try several approaches in
the laboratory in order to find the most efficient or successful
route.