RESUMO
Two approaches have been developed for the enantioselective Reformatsky reaction of ethyl iododifluoroacetate with ketones to form a quaternary carbon centre using (1R,2S)-1-phenyl-2-(1-pyrrolidinyl)-1-propanol as the chiral ligand. Good yields and high enantioselectivities (80-91% ee) were achieved with a range of alkyl aryl ketones in a convenient one-pot protocol using ethyl iododifluoroacetate and diethylzinc to form the difluorinated Reformatsky reagent homogeneously. In the traditional two-step Reformatsky reaction using the preformed Reformatsky reagent generated from ethyl iododifluoroacetate and zinc dust, good yields and good enantioselectivities (75-84% ee) were also obtained.
Assuntos
1-Propanol/química , Fluoracetatos/química , Iodo/química , Cetonas/química , Halogenação , Ligantes , Modelos Moleculares , Compostos Organometálicos/química , EstereoisomerismoRESUMO
The first enantioselective Reformatsky-type reaction of ethyl iodofluoroacetate has been accomplished with alkyl aryl ketones. High diastereoselectivities and excellent enantioselectivities for the major diastereomer (93-95% ee) were achieved with large alkyl groups. For smaller alkyl groups the diastereoselectivities were moderate, but excellent enantioselectivities were obtained for both diastereomers (79-94% ee).