Asymmetric Radical Addition of TEMPO to Titanium Enolates
作者:Phillip J. Mabe、Armen Zakarian
DOI:10.1021/ol403398u
日期:2014.1.17
A mild method for α-hydroxylation of N-acyl oxazolidinones by asymmetricradicaladdition of the 2,2,6,6-tetramethylpiperidine N-oxy (TEMPO) radical to titanium enolates was developed. The high diastereoselectivity and broad scope of the reaction show synthetic utility for the α-hydroxylation of substrates that are not tolerant to strongly basic conditions.
Here, we present a new stereoselective alkylation of titanium(IV) enolates of chiral N-acyl oxazolidinones with tert-butyl peresters from Cα-branched aliphatic carboxylic acids, which proceeds through the decarboxylation of the peresters and the subsequent formation of alkyl radicals to produce the alkylated adducts with an excellent diastereoselectivity. Theoretical calculations account for the observed