1. RETROSYNTHETIC APPROCH TO ORGANIC SYNTHESIS Prof. Dr. Shaikh S. Nizami Department of Chemistry University of Karachi

2. BASIC CONCEPTS (Part 1)

4. READING MATTERIALS

11. Reasons for synthesizing Organic Compound 3. To prepare specific compounds to study reaction mechanisms or biological metabolism e.g. labelled compounds 4. For the intellectual challenges – new problems demand new solutions and can lead to the development of NEW CHEMISTRY, reagents, etc .

12. SOME FASCINATING COMPOUNDS

15. ARROW NOTATION Simple reaction arrow “ reacts to give” Delocalisation arrow “ two different ways to draw the same delocalised structures” Equilibrium arrow Curved arrow “ two structures are interconverting” “ motion of two electrons” Fish-hook arrow “ motion of one electron” Retrosynthesis arrow “ could be made from”

16. RETROSYNTHESIS It is reverse of the synthetic steps We have a reliable reaction in mind

19. JIGSAW PUZZLE (Target Puzzle)

20. PUZZLE (Disconnection)

21. DISCONNECTION OF C-C SYNTHONS

26. Retrosynthetic analysis, Synthons & Synthetic equivalents R — R  ……………………………………………………………………… R + + R - R - + R +     TM RBr, RI, ROMe, ROTs RMgBr, RLi, LiCuR 2 Synthons Synthetic equivalents

29. RETOSYNTHETIC ANALYSIS Hawthorn perfume

32. 1 st RETROSYNTHETIC ANALYSIS CH 3 CH 2 OH

33. SYNTHESIS

34. 2 nd RETROSYNTHETIC ANALYSIS CH 3 CH 2 OH & SYNTHESIS

35. 3 rd RETROSYNTHETIC ANALYSIS CH 3 CH 2 OH & SYNTHESIS

36. 4 th RETROSYNTHETIC ANALYSIS CH 3 CH 2 OH & SYNTHESIS