Van Leusen reaction
Van Leusen reaction | |||||||||
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Named after | Daan Van Leusen Albert M. Van Leusen | ||||||||
Reaction type | Substitution reaction | ||||||||
Reaction | |||||||||
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Organic Chemistry Portal | van-leusen-reaction | ||||||||
The Van Leusen reaction is the reaction of a ketone with TosMIC leading to the formation of a nitrile. It was first described in 1977 by Van Leusen and co-workers.[1] When aldehydes are employed, the Van Leusen reaction is particularly useful to form oxazoles and imidazoles.
Mechanism
The
carbonyl is followed by 5-endo-dig cyclisation (following Baldwin's rules
) into a 5-membered ring.
Van Leusen oxazole synthesis | |||||||
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Named after | Daan Van Leusen Albert M. Van Leusen | ||||||
Reaction type | Ring forming reaction | ||||||
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Organic Chemistry Portal | van-leusen-oxazole-synthesis | ||||||
If the substrate is an aldehyde, then
tosyl leaving group
can occur readily. Upon quenching, the resulting molecule is an oxazole.
Van Leusen imidazole synthesis | |
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Named after | Daan Van Leusen Albert M. Van Leusen |
Reaction type | Ring forming reaction |
Identifiers | |
Organic Chemistry Portal | van-leusen-imidazole-synthesis |
If an
aldimine is used, formed from the condensation of an aldehyde with an amine, then imidazoles can be generated through the same process.[2]
When ketones are used instead, elimination cannot occur; rather, a
tautomerization
process gives an intermediate which after a ring opening process and elimination of the tosyl group forms an N-formylated alkeneimine. This is then solvolysed by an acidic alcohol solution to give the nitrile product.
References
- .
- PMID 16018616.