Asymmetric aldol reaction using boron enolates.
The protocol for the preparation of boron enolates and their subsequent reaction with aldehydes is described, providing convenient access to beta-hydroxy ketones in good yields and with high stereoselectivities. The reaction consists of three steps: first, the ketone is rapidly converted to the corresponding boron enolate, by exposure to a chlorodialkylborane and tertiary amine base, which is then reacted in situ with the aldehyde. Finally, oxidative workup of the resultant boron aldolate provides aldol adduct. The reaction procedure requires approximately 28 h to complete over a 2-d period, consisting of 5 h to set up the reaction, whereupon the reaction mixture is left at -20 degrees C overnight (16 h), followed by 7 h for workup and purification.
Cergol
Katie M
KM
School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
Coster
Mark J
MJ
D000447:Aldehydes / Q000737:chemistry*; D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry; D010084:Oxidation-Reduction
D000447:Aldehydes; D001896:Boron Compounds; D007659:Ketones; C116609:3-hydroxybutanal