The first example of enamine-Lewis acid cooperative bifunctional catalysis: application to the asymmetric aldol reaction.
(-)-Sparteine directed lithiation of N-Boc-pyrrolidine, alkylation with chloromethylboronate pinacol ester and acid-based deprotection provides homoboroproline HX salt in 94% ee, which is then an efficient enamine-type pyrrolidine catalyst in an asymmetric aldol reaction when neutralised and especially when esterified in situ with a tartrate ester, for example, providing 90% ee of the aldol adduct derived from acetone and p-nitrobenzaldehyde.
Arnold
Kenny
K
Department of Chemistry, Science Laboratories, Durham University, South Road, Durham, UK.
Batsanov
Andrei S
AS
Davies
Bryan
B
Grosjean
Christophe
C
Schütz
Thorben
T
Whiting
Andrew
A
Zawatzky
Kerstin
K
D000143:Acids / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D002384:Catalysis; D058116:Lewis Acids / Q000737:chemistry*
D000143:Acids; D000447:Aldehydes; D000588:Amines; D058116:Lewis Acids; C116609:3-hydroxybutanal