Use of alkyl 2,4,6-triisopropylbenzoates in the asymmetric homologation of challenging boronic esters
作者:Robin Larouche-Gauthier、Catherine J. Fletcher、Irantzu Couto、Varinder K. Aggarwal
DOI:10.1039/c1cc14469c
日期:——
(-)-Sparteine induced lithiation of primary 2,4,6-triisopropylbenzoates and subsequent homologation of boronicesters is reported. A comparative study with lithiated N,N-diisopropylcarbamates has demonstrated the superiority of the hindered benzoate.
Stereocontrolled Synthesis of β-Amino Alcohols from Lithiated Aziridines and Boronic Esters
作者:Frank Schmidt、Florian Keller、Emeline Vedrenne、Varinder K. Aggarwal
DOI:10.1002/anie.200805272
日期:2009.1.26
β‐Amino alcohols have been prepared with high selectivity by the addition of lithiatedaziridines to boronic esters. The regioselectivity of lithiation for aryl aziridines is sensitive to the reaction conditions and to the base employed. This response was exploited to give either class of β‐amino alcohols (see scheme; Boc=tert‐butoxycarbonyl, Bus=tert‐butylsulfonyl, LTMP=lithium 2,2,6,6‐tetramethylpiperidide
Vinyl boron ate complexes of enantioenriched secondary alkyl pinacolboronic esters undergo stereospecific radical-induced 1,2-migration in radical polar crossover reactions. In this three-component process various commercially available alkyl iodides act as radical precursors and light is used for chain initiation. Subsequent oxidation and protodeborylation leads to valuable α-chiral ketones and chiral