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Synfacts 2014; 10(1): 0081
DOI: 10.1055/s-0033-1340368
Metal-Mediated Synthesis
© Georg Thieme Verlag Stuttgart · New York

Lithiation–Borylation of Secondary Alkyl Benzoates

Contributor(s):
Paul Knochel
,
Andreas K. Steib
Pulis AP, Blair DJ, Torres E, Aggarwal VK * University of Bristol, UK
Synthesis of Enantioenriched Tertiary Boronic Esters by the Lithiation/Borylation of Secondary Alkyl Benzoates.

J. Am. Chem. Soc. 2013;
135: 16054-16057
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Further Information

Publication History

Publication Date:
13 December 2013 (online)

 
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Key words

lithium - boron - boronic esters

Significance

Against common wisdom, Aggarwal and co-workers have now shown that secondary 2,4,6-triisopropyl benzoates (TIP esters) can be deprotonated at –60 °C using a combination of s-BuLi and TMEDA in cyclopentyl methyl ether (CPME). The resulting lithium reagents were ­allowed to react with various neopentyl boronic esters which after 1,2-metalate rearrangement and oxidation furnished a range of tertiary alcohols in good enantioselectivity.


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Comment

This lithiation reaction cannot be performed in THF. Simply switching from THF to diethyl ether increased the yield of the lithiated benzoate. The extent of lithiation was increased further by using CPME. Interestingly, the subsequent borylation reaction occurs with complete retention of configuration.


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