CY5014 : REACTIVE INTERMEDIATES AND CONCERTED REACTIONS

Course Objectives: To learn the involvement of reactive intermediates and understand their structure and reactivity through various organic reactions. To learn and understand the orbital interactions (Woodward Hoffmann rules) in concerted reactions. Learn to apply concerted and stepwise reactions in organic synthesis

Learning Outcomes: At the end of the course, the learners should be able to:

Comprehend the structure-reactivity pattern of reactive intermediates involved in organic reactions

Comprehend the orbital interactions and orbital symmetry correlations of various pericyclic reactions

Write the mechanism of organic reactions involving reactive intermediates and concerted processes

Apply these reactions in organic synthesis

Course Contents:

Carbanions: C-X bond (X = C, O, N) formations through the intermediacy of Carbanions: Chemistry of enolates and enamines, Kinetic and Thermodynamic enolates, Lithium and boron enolates in aldol and Michael reactions, Alkylation and acylation of enolates, Nucleophilic additions to carbonyls; Organolithium, Organomagnesium, Organozinc, Organocopper reagents (restricted to 1,4-addition) in synthesis, Name reactions under carbanion chemistry – Claisen, Dieckmann, Knoevenegal, Stobbe, Darzen, Acyloin condensations, Shapiro reaction, Julia olefination etc. Ylids: Chemistry of Phosphorous and Sulfur ylids – Wittig and related reactions, Peterson olefination, etc.

Carbocation: Structure and stability of carbocations, Classical and non-classical carbocations, Neighbouring group participation and rearrangements including Wagner-Meerwein, Pinacol-pinacolone, semi-pinacol rearrangement, C-C bond formation involving carbocations, Oxymercuration, halolactonisation.

Carbenes and Nitrenes: Structure of carbenes, generation of carbenes, addition and insertion reactions, rearrangement reactions of carbenes such as Wolff rearrangement, generation and reactions of ylid by carbenoid decomposition, Structure of nitrene, generation and reactions of nitrene and related electron deficient nitrogen intermediates, Curtius, Hoffmann, Schmidt, Beckmann rearrangement reactions.

Radicals: Generation of radical intermediates and its (a) addition to alkenes, alkynes (inter & intramolecular) for C-C bond formation and Baldwin’s rules (b) fragmentation and rearrangements. Name reactions involving radical intermediates such as Barton deoxygenation and decarboxylation, McMurry coupling, etc.

Pericyclic Reactions: Classification, electrocyclic, sigmatropic, cycloaddition, chelotropic and ene reactions, Woodward Hoffmann rules, Frontier Orbital, and Orbital symmetry correlation approaches, examples highlighting pericyclic reactions in organic synthesis such as Claisen, Cope, Diels-Alder and Ene reactions (with stereochemical aspects), dipolar cycloadditions and their utility in organic synthesis.

Text Books:

1. A. Carey and R. A. Sundberg, Advanced Organic Chemistry, Part B: Reactions and Synthesis, 5th edition, Springer, New York, 2007.
2. Carruthers and I. Coldham, Modern methods of Organic Synthesis, First South Asian Edition 2005, Cambridge University Press.
3. March and M. B. Smith, March’s Advanced Organic Chemistry: Reactions, Mechanisms, and Structure, 6th Edition, Wiley, 2007.
4. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1976.
5. Sankararaman, Pericyclic Reactions- A text Book, Wiley VCH, 2005