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

Molecules

Adeem Mahmood¹  Hamad Z. Alkhathlan¹  Saima Parvez³  Merajuddin Khan¹  Sohail A. Shahzad² 

[1] Department of Chemistry, College of Science, King Saud University, Riyadh 11451, Saudi Arabia; E-Mail:;Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan; E-Mail:;School of Medicine, Shandong University, Jinan 250012, China; E-Mail:

关键词: lithiation;    borylation;    allylation;    chelation;   

DOI  :  10.3390/molecules20069890

来源: mdpi

【 摘 要 】

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.

【 授权许可】

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© 2015 by the authors; licensee MDPI, Basel, Switzerland.