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Open AccessArticle

Chelation-Assisted Substrate-Controlled Asymmetric Lithiation-Allylboration of Chiral Carbamate 1,2,4-Butanetriol Acetonide

Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia
Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan
School of Medicine, Shandong University, Jinan 250012, China
Authors to whom correspondence should be addressed.
Academic Editor: Jean Jacques Vanden Eynde
Molecules 2015, 20(6), 9890-9905;
Received: 5 April 2015 / Revised: 19 May 2015 / Accepted: 20 May 2015 / Published: 28 May 2015
(This article belongs to the Section Organic Chemistry)
The lithiation of 2-(2,2-dimethyl-1,3-dioxolan-4-yl)ethyl diisopropylcarbamate (1) is achieved freely by sec-butyllithium in diethylether with high lk-diastereoselectivity: the bicyclic chelate complexes 3a and 3b are reacted with electrophiles to form optically active precursors 4a and 4b with >95% diastereoselectivity. In addition, tertiary diamines can undergo an external complexation in contest with the internal oxygen ligand, leading to improved stereoselectivities. The further reactions of lithiated carbamates with trans alkenyl-9-BBN derivatives after 1,2 metallate rearrangements, gave the key intermediate α-substituted allylic boranes 7. Subsequent allylboration of aldehydes gave (Z)-anti-homoallylic alcohols 8 in good yield and excellent d.r. View Full-Text
Keywords: lithiation; borylation; allylation; chelation lithiation; borylation; allylation; chelation
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MDPI and ACS Style

Mahmood, A.; Alkhathlan, H.Z.; Parvez, S.; Khan, M.; Shahzad, S.A. Chelation-Assisted Substrate-Controlled Asymmetric Lithiation-Allylboration of Chiral Carbamate 1,2,4-Butanetriol Acetonide. Molecules 2015, 20, 9890-9905.

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