Enols and Enolates – Part 2 | Organic Chemistry 3

Additional reactions of enols and enolates are studied in this chapter: halogenation of aldehydes and ketones, 1,2- and 1,4-additions of unsaturated carbonyls by organometallic reagents, Michael addition, Robinson annulation

Halogenation of Aldehydes and Ketones


Mechanism:

  1. Enolization:


     
  2. Halogen attack followed by deprotonation:

1,2- and 1,4-additions by Organometallic Reagents


Organolithium reagents (RLi): 1,2-addition
Gilman reagents (R2CuLi): 1,4-addition
Grignard reagents (RMgBr): 1,2 or 1,4-addition depending on reagent and substrate structure

Michael Addition


Mechanism:

Robinson Annulation


Mechanism:

  1. Michael addition:


     
  2. Intramolecular aldol condensation:


     
  3. Aldol dehydration: