Highly Stereoselective Samarium(II) Iodide-Mediated Aldol Reactions of Acylaziridines with Aldehydes

摘要

The samarium(II) iodide-mediated Stereoselective aldol reactions of acylaziridines with aldehydes are described.beta-Amino-beta'-hydroxy ketones were synthesized in high yields by the aldol reaction of aldehydes with samarium enolates generated by aziridine-fragmentation of aziridinyl ketones with two moles of samarium(II) iodide.By the choice of an appropriate nitrogen protecting group,depending on the substituent at C-3 position of aziridinyl ketone,anti,anti-beta-ami-no-beta'-hydroxy ketones were diastereoselectively obtained among the four possible diastereomers.Further,enantiomeri-cally pure anti,anti-beta-amino-beta'-hydroxy ketones were successfully obtained by this aldol reaction when chiral aziridinyl ketones were used.In addition,delta-amino-beta'-hydroxy-beta,gamma-unsaturated esters were also synthesized in high yields by the aldol reaction of aldehydes with samarium enolates generated by aziridine-fragmentation and olefin-migration of gamma,beta-aziridinyl-alpha,beta-unsaturated esters using two moles of samarium(II) iodide.This aldol reaction proceeded with complete alpha-regioselectivity and formed (E)-olefin selectively.By introducing chiral oxazolidin-2-one auxiliary to gamma,beta-aziridinyl-alpha,beta-unsaturated carbonyl system,this reaction was extended successfully to the asymmetric reaction and enantiomeri-cally pure syn-delta-amino~beta'-hydroxy-beta,gamma-unsaturated esters were obtained in high yields.