Department of chemistry
PONDICHERRY UNIVERSITY
Department of chemistry
CHEM562 Approaches to organic synthesis
December 2023
Note:
1.This is a take home examination
2.You can answer the questions from the discussions in the class room
3.Give reference, if you use any web source
4.Submit on or before 22nd December 5.30 pm.
5.Submit your answer to my research scholars Mr. G. Adhithya or Mr. K. Sriram6.Q4 is mandatory to earn A or A+ in term end examination.
7.If identical answers for more than one question in any answer script is noticed all such answer scripts will be awarded zero.
1.Target molecules A, B and C are synthesised from simple synthons. One of the synthons is shown in S1. By retrosynthetic analysis, identify the other reactant(s), reliable reactions and mechanism of the reaction(s).
ABC
S1
2.Carbonyl compound in +1 oxidation state is an ideal substrate for tying up two nucleophilic reactants for building up molecular framework and cyclization. Give five examples. Give reference for each example you cite.
3.Single reactant replacement (SRR) strategy is a logic based approach in MCR for switching the scaffold. SRR strategy involves replacing one of the building blocks in known MCR by another component which mimics the key chemical reactivity of that reactant with additional functionality. Given below are the two famous IMCR reactions. Ugi 4 CR (U4CR) is an example of Single Reactant Replacement (SRR) strategy applied to Passerine 3CR (P3CR).
(i) Give example for both P3CR and U4CR. Give the complete reaction scheme, mechanism and reference.
(ii) Applying the same SRR principle to the 4CR given below, scaffolds A to D were synthesised. Write mechanism for the transformation. The reactants used in MCR are described as building blocks. In the scaffolds A to D identify the SRR building block and identify the reaction centre / functional group leading to the diverse skeletal outcome
Scheme 1
4.It is assumed that in an advanced organic chemistry course, a discussion on organic reactions as reaction between an electrophile and nucleophile sounds too trivial. As a student of advanced course on Approaches to organic synthesis you are suggested to choose any recently published research on organic synthesis of new organic molecule(s), (not on new reagent or method development) and do critical analysis of the paper and report on the following points.
1.Title of the paper
2.Reference
3.Abstract
4.Scheme
5.Mechanism
6.Role of each reactant used in the reaction including solvent.
You are required to highlight the innovation in the scheme (Other than a bond formed between positively and negatively polarised reaction centres.
5.For the scaffolds given below choose any three and answer the following points.
(i)Stepwise retrosynthetic analysis. You are required to describe the logic of each disconnection.
(ii)You are required to identify a reliable reaction for each disconnection and analyse the reactivity/selectivity issues and comment on how you will address the issue.
(iii)Write the complete synthetic protocol specifying reagents and mechanism for each step.