131899-77-9Relevant academic research and scientific papers
A short and efficient synthesis of (+)-prelactone B
Dias, Luiz C.,Steil, Leonardo J.,Vasconcelos, Valeria De A.
, p. 147 - 150 (2004)
The asymmetric total synthesis of (+)-prelactone B, a biologically important natural β-hydroxy-δ-lactone derivative that contains a 2,3-trans-dialkylpyran ring system, is described. This approach involves the use of a very efficient oxazolidinone-mediated anti-aldol reaction, and a diastereoselective coupling between a ketene silyl acetal with an aldehyde followed by lactonization.
Lithium Amino Alkoxide-Evans Enolate Mixed Aggregates: Aldol Addition with Matched and Mismatched Stereocontrol
Jermaks, Janis,Tallmadge, Evan H.,Keresztes, Ivan,Collum, David B.
supporting information, p. 3077 - 3090 (2018/03/08)
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 are determined spectroscopically. Rate and computational studies provide a viable mechanistic and stereochemical model based on the direct reaction of the 3:1 mixed tetramers, but they raise unanswered questions for the 2:2 mixed aggregates.
The exceptional chelating ability of dimethylaluminum chloride and methylaluminum dichloride. The merged stereochemical impact of α- and β-stereocenters in chelate-controlled carbonyl addition reactions with enolsilane and hydride nucleophiles
Evans,Allison,Yang,Masse
, p. 10840 - 10852 (2007/10/03)
A systematic investigation of the stereoselectivity in Lewis acid-promoted (Mukaiyama) aldol reactions of achiral unsubstituted enolsilanes and chiral β-hydroxy aldehydes proceeding under conditions favoring chelation control is presented. Good stereocontrol can be realized for enolsilane aldol reactions of β-alkoxy and β-silyloxy aldehydes bearing only an α- or a β-stereogenic center. Examination of the chelated intermediates for α,β-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the α- and β-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing stereocontrol elements at the α- and β-positions exhibit variable and unpredictable selectivity.
The chromium-reformatsky reaction: Anti-selective evans-type aldol reactions with excellent inverse induction at ambient temperature
Gabriel, Tobias,Wessjohann, Ludger
, p. 4387 - 4388 (2007/10/03)
anti-Aldol products are available in a two step, one pot reaction of 4-substituted oxazolidone, 2-bromopropionyl halide, chromium dichloride and an aldehyde. The diastereofacial selection (induction) is opposite to those of boron Evans enolates, i.e. the
