Advanced Organic Chemistry/ Organic Synthesis – CH 621...
Transcript of Advanced Organic Chemistry/ Organic Synthesis – CH 621...
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Advanced Organic Chemistry/ Organic Synthesis – CH 621
Protecting Groups
Bela TorokDepartment of Chemistry
University of Massachusetts BostonBoston, MA
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Protecting Groups – Strategy
To protect one sensitive group, while the “active” group should
remain unchanged.
- (Selective reactions)
- Protecting groups, when the above is not possible
Ideal protection:
- Introduce under mild conditions
- Stable under the target reaction conditions
- Removable under mild conditions
- Orthogonal protection
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Protecting Groups – Alcohols
Protection of Alcohols
Formation of ethers
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Protecting Groups – Alcohols
Protection of Alcohols
Formation of silyl ethers
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Protecting Groups – Alcohols
Protection of Alcohols
Formation of esters
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Protecting Groups – Alcohols
Protection of Alcohols
Formation of esters
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Protecting Groups – Carboxylic acids
Formation of esters
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Protecting Groups – Carboxylic acids
Formation of orthoesters
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Protecting Groups – Thiols
Formation of ethers
Avoid oxidativeconditions(S oxidation)
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Protecting Groups – Aldehydes and Ketones
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Protecting Groups – 1,2- and 1,3-diols
Acetals
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Protecting Groups – Amines
N-alkylation
Usually:- N-benzyl- N-trityl- N-allyl
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Protecting Groups – Amines
N-Acylation
Usually:- N-benzoyl- N-acetyl- N-trifluoroacetyl
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Protecting Groups – Amines
Formation of carbamates
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples
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Protecting Groups – Examples