Asymmetric Aldol Type Reactions of Acetate Imide Enolates

Samarium Iodide-Promoted Asymmetric Reformatsky Reaction of 3-(2-Haloacyl)-2-oxazolidinones with Enals

“…Furthermore, they are valuable synthetic scaffolds for the synthesis of complex target molecules, as was exemplified in the total synthesis of pleuraspiroketals A, B, (−)-clavosolide A, B, bistramide K, solomonamide, azaspirene, dolatrienoic acid, and ferrulactone . The β-hydroxy-γ-alkenyl-ketone unit has been previously accessed via stereoselective aldol reactions using Evans oxazolidinones. − …”

Promotion of a Ti-Mediated Mannich Reaction by a Proton Source

“…In support of a drug development program, we began evaluating a similar transformation, where we were interested in accessing β-amino acid derivative 3a as a useful synthetic intermediate. Our initial experiment showed that treatment of aldimine 1 with in situ generated Ti-enolate of phenyl oxazolidone 2 ( 2-enol-Ti ) at −40 °C in CH 2 Cl 2 , followed by quenching the reaction with aqueous HCl at −20 °C afforded the desired Mannich adducts, with concomitant removal of the TMS group, in a 5:1 anti/syn diastereoselectivity and a 52% combined yield (Scheme ). Initial attempts to optimize the reaction did indeed afford variable chemical yields and poor reproducibility, even when the reaction was quenched at low temperatures (<−20 °C).…”

Stereoselectivity in Aldol Reactions of Chiral N-Acyl Selones

“…Although rare, “non-Evans” aldol reactions have been reported. The Crimmins and Yan groups recently reported on “non-Evans” aldols that employ thiocarbonyl-based CDA's. Table illustrates the range of products that can be obtained using our selenium-based CDA's.…”