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Variation in sites of lithiation of substituted N-benzylpivalamides and N'-benzyl-N,N-dimethylureas: application in synthesis

El-Hiti, Gamal, Smith, Keith, Hegazy, Amany Saber, Shalabi, Ahmed Fekri and Kariuki, Benson 2009. Variation in sites of lithiation of substituted N-benzylpivalamides and N'-benzyl-N,N-dimethylureas: application in synthesis. Arkivoc Online Journal of Organic Chemistry , pp. 266-300.

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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.

Item Type: Article
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Uncontrolled Keywords: Directed ortho-lithiation; electrophilic substitution; substituted benzylamines; synthesis; side-chain lithiation
Additional Information: Part (xiv): General Papers. Graphical abstracts
Publisher: Arkat USA Inc
ISSN: 1551-7004
Date of First Compliant Deposit: 30 March 2016
Last Modified: 04 Jun 2017 02:51
URI: http://orca-mwe.cf.ac.uk/id/eprint/12725

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