Enantioselective addition of β-functionalized allylboronates to aldehydes and aldimines. Stereocontrolled synthesis of α-methylene-γ-lactones and lactams
We report results regarding the development of condensations of chiral β-alkoxycarbonylallylboronates on aldehydes and imines. These allylboronates add in a highly enantioselective and diastereospecific manner to afford biologically and synthetically useful chiral α-methylene-γ-butyrolactones and lactams. The nature of the electrophile (aldehyde vs imine) is shown to have a dramatic influence on the
Asymmetric synthesis using a new chiral β-functionalized allylboronate derived from endo-2-phenyl-exo-2,3-bornanediol: Preparation and reactions with aldehydes
The allylboron reagent 4 prepared from endo-2-phenyl-exo-2,3-bornanediol reacts with achiral aldehydes to give homoallylic alcohols in good yields and high enantioselectivity (70–85% ee). This new reagent also exhibits good levels of matched and mismatched diastereoselection in reaction with chiralaldehydes. A mechanism is proposed to explained the high regio and stereoselectivity of this carboalkoxyallylboration