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- Title
Variation in sites of lithiation of substituted N-benzylpivalamides and N'-benzyl-N,N-dimethylureas: application in synthesis.
- Authors
Keith Smith; El-Hiti, Gamal A.; Hegazy, Amany S.; Fekri, Ahmed; Kariuki, Benson M.
- Abstract
Directed lithiation of various substituted benzylamines takes different courses depending on the substituents at nitrogen and on the aryl ring and/or the nature of the alkyllithiums. Lithiation of N-benzylpivalamide with t-BuLi gives a mixture of ring (2-position) and side-chain lithiated species, but the 2-lithiated isomer can be obtained cleanly via bromine-lithium exchange of N-(2-bromobenzyl)pivalamide. N′-Benzyl-N,N-dimethylurea, N′-(4-substituted benzyl)-N,N-dimethylureas and N-(4-substituted benzyl)pivalamides give 2-lithiated derivatives directly with t-BuLi at -78 °C. By contrast, lithiation of N-(2-methoxybenzyl)pivalamide occurs at the 6-position, ortho- to the methoxy group, while lithiation of N′-(2-methoxybenzyl)-N,N-dimethylurea gives a mixture of 2- and 6-lithiated species. All organolithiums are converted in high yields to their corresponding substitution products on reactions with various electrophiles.
- Subjects
ELECTROPHILES; NITROGEN; NUCLEAR isomers; BROMINE; ORGANOLITHIUM compounds; HETEROCYCLIC compounds; LITHIUM
- Publication
ARKIVOC: Online Journal of Organic Chemistry, 2009, p266
- ISSN
1551-7004
- Publication type
Article