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Boc Protection

(Boc2O + Base)







Mechanism:



Boc protection mechanism using base


Steps:

  1. The amine attacks a carbonyl site on di-tert-butyl dicarbonate (Boc2O) resulting in tert-butyl carbonate leaving as a leaving group.
  2. The base (usually TEA or DIEA) picks up the proton from the protonated amine.
  3. Tert-butyl carbonate breaks down into CO2 (gas) and tert-butoxide.

Key Points:

  1. The CO2 gas that forms during the rxn should be allowed to escape. Don't run boc protections in closed systems.
  2. Base isn't needed for a boc protection rxn to progress (see Boc Protection Boc2O).
  3. Tert-butoxide is actually a stronger base than TEA (or DIEA) therefore in the end the proton should end up on tert-butoxide forming tert-butanol.



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