به نام خدا Advanced Organic Chemistry روشهای 1 سنتز مواد آلی Dr Morteza Mehrdad University of Guilan, Department of Chemistry, Rasht, Iran m-mehrdad@guilan.ac.ir
References: 1. Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry: Reactions and Synthesis (Part B), 5th ed., Springer, 2007. 2. Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry: Structure and Mechanisms (Part A), 5th ed., Springer, 2007. 3. House, H. O. Modern Synthetic Reactions, 2nd Edition, W. A. Benjamin, Menlo Park, 1972. 4. Smith, M. B. Organic Synthesis, 2nd edition McGraw-Hill, NY, 2000. 5. Warren, S. Organic Synthesis: The Disconnection Approach, John Wiley & Sons, New York, 1991. 6. Nicolaou, K. C. and Sorensen, E. J. Classics in Total Synthesis: Targets, Strategies and Methods, VCH Publishers, New York, 1996. 7. Fuhrhop, J. H.; Li, G. Organic Synthsis, John Wiley & Sons, New York, 2003. 8. Pine, S. H.; Hendrickson, J. B.; Cram, D. J.; Hammond, G. S. Organic Chemistry, McGraw-Hill Inc., Tokyo, 1980.
Synthesis (from the Greek word synthesis [ Suntithenai ] = [Sun(together) + tithenai(to put)]= the process of putting together) Synthetic chemistry synthetic organic chemistry synthetic inorganic chemistry is the science of constructing molecules from atoms and/or (usually) simpler molecules. 3
organic synthesis synthetic organic chemistry science of synthetic chemistry chemical synthesis is the process by which a particular molecule is synthesized in the laboratory. total synthesis is the chemical synthesis of a molecule, usually a natural product, from relatively simple starting materials 4
ORGANIC SYNTHESIS Target Oriented (Total Synthesis) Methods Oriented Natural Products Designed Molecules Reagents Catalysts Synthetic Strategies Synthetic Tactics Materials Science Interesting Molecules Biologically Interesting Molecules Theoretically Interesting Molecules Medically Interesting Molecules 5
Organic synthesis 1. Design of a synthesis 2. Constraction reactions 3. Functional group interconversions 4. Stereochemistry 6
1. Design of synthesis a. Initial consideration in synthesis design Carbon skeleton Functional group (Synthon) b. The retro-synthetic approach c. Starting materials (target molecule) (Disconnetion) 7
d. Yield and reaction specificity overall yield is the mathematical product of the yields of all the individual steps Overall yield = 100 x (1 x 0.87 x 0.67 x 0.55) = %32 1. minimum number of steps 2. a good precedent of high yields 3. competing reactions are minimal 8
2. Constraction reactions a. Half-reactions and recognition patterns b. Annelation reactions c. Fragmentation reactions 9
1 Nucleophilic Half-Reactions (Products) (Starting Materials) Organometallic Aldol or Claisen (enolate reactions) Friedel- Crafts 2 Electrophilic Half-Reactions (Products) (Starting Materials) Alkylation Carbonyl addition Conjugated addition 10
Construction chart of the Major half-reactions. 2 2 2 2 4 3 3 2 3 3 3 3 3 3 5 2 2 4 2 2 11
span = A relation between the functional groups which are usually the key to bond-forming processes 12
Recognition patterns between span and constructions 13
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2. Constraction reactions a. Half-reactions and recognition patterns b. Annelation reactions c. Fragmentation reactions 16
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2. Constraction reactions a. Half-reactions and recognition patterns b. Annelation reactions c. Fragmentation reactions Reactions which make carbon-carbon bonds are construction reactions. those that cleave carbon-carbon bonds are called fragmentation reactions: Ozonolysis is an important fragmentation used as a source of carbonyl groups. 18
The other important fragmentation is the decarboxylation of -keto acids and -diacids 19
3. Functional group interconversions a. Altering functional groups b. Removing functional groups c. Selectivity d. Protecting groups Hydroxy and carbonyl group interconversions 20
Some interaction versions of the carboxylic acid family and other terminal groups. 21
3. Functional group interconversions a. Altering functional groups b. Removing functional groups c. Selectivity d. Protecting groups Common methods for Removing functional groups. 22
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3. Functional group interconversions a. Altering functional groups b. Removing functional groups c. Selectivity d. Protecting groups 1. Hydride reductions: Sodium borohydride generally reduces only ketones, aldehydes, and acyl halides; lithium aluminum hydride reduces those compounds as well as compounds of the carboxylic acid family. 2. Catalytic hydrogenation 3. Saturated carbons 4. Cyclic reactions 5. Carbonyl groups 6. Carbon-carbon double bonds 24
3. Functional group interconversions a. Altering functional groups b. Removing functional groups c. Selectivity d. Protecting groups 25
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4. Stereochemistry A target molecule with n chiral centers has 2 n possible stereoisomers. Many modern syntheses begin with one stereoisomer of a naturally occurring material such as a terpene, a carbohydrate, or an amino acid. In such sequences it is very important to utilize reactions of known stereospecificity. The major reactions which offer stereochemical control: 28
Bulky reagent More stable Eq isomer Less stable Ax isomer 29
enolization more stable isomer 30
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