Application of the Silicon-Tether Strategy for Controlling the Regioselectivity and Diastereoselectivity of Intramolecular Nitrone Cycloadditions for Aminopolyol Synthesis
Highly regioselective and diastereoselective intramolecular chiral nitronecycloaddition reactions with a vinyl group tethered by a silicon atom have been developed as a general method for the synt...
Lithium Amino Alkoxide–Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol
作者:Janis Jermaks、Evan H. Tallmadge、Ivan Keresztes、David B. Collum
DOI:10.1021/jacs.7b13776
日期:2018.2.28
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries
germanium(II) iodide with potassium metal, was found to promote the Reformatskyreaction effectively under mild conditions. In the presence of activated germanium metal, the reactions of alpha-bromo ketones 2a and 2b and alpha-bromo imides 2e and 2f with benzaldehyde (1a) proceeded smoothly to give the corresponding beta-hydroxy carbonyl compounds 3a, 3b, 3e and 3f, respectively, in good yields and with
Bifunctional chiral auxiliaries 7: Aldol reactions of enolates derived from 1,3-diacyl-imidazolidine-2-thiones and 1,3-diacylimidazolidin-2-ones
作者:Stephen G. Davies、Alison J. Edwards、Gary B. Evans、Andrew A. Mortlock
DOI:10.1016/s0040-4020(01)89691-5
日期:——
Dibutylboron enolates of 1,3-diacylimidazolidine-2-thiones and 1,3-diacylimidazolidin-2-ones undergo highly syn-stereoselective aldol reactions with aldehydes to allow elaboration of both acyl sidechains. The reaction is proposed to occur via sequential enolisation rather than via a bisenolate and the stereochemistry of the product was elucidated by both X-ray crystallography and reductive cleavage