ON THE ASYMMETRIC INDUCTION INVOLVING LITHIUM ENOLATES OF 1-MENTHYLPROPIONATE
The stereoselectivities of the reaction between 1-menthylpropionate 1 with LDA under standard kinetic conditions depend on the solvent.The Z-enolate 2a predominates in LDA/THF (Z/E=7.5/2.5) while the E-enolate 3a is the main product in LDA/THF/hexane (E/Z=8/2).The mixture of these enolates (E/Z=8/2) was allowed to react with allylbromide, benzaldehyde and MoOPH respectively.The higher ?-facial diastereoselection was obtained from MoOPH (d.e.=60percent).
Ribeiro, Leny P.,Antunes, Octavio A. C.,Bergter, Lothar,Costa, Paulo R. R.
p. 1873 - 1874
(2007/10/02)
Highly diastereoselective reduction of (-) menthylphenylglyoxalate and (-) menthylpyruvate using new hindered lithiumtrialkoxyaluminohydrides
Reduction of the keto group of (-) menthylphenylglyoxalate and (-) menthyl pyruvate can be achieved with high diastereoisomeric excess (80-90percent) using newly synthesized hindered lithium trialkoxyaluminium hydrides in THF at -78 deg C.Hindered borohydrides such as lithium trisiamylborohydride reduce those ketoesters with a lower diastereoselectivity.
Boireau, G.,Deberly, A.
p. 771 - 774
(2007/10/02)
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