Improved Methodology for the Preparation of Chiral Amines
Improved Methodology for the Preparation of Chiral Amines
Improved Methodology for the Preparation of Chiral Amines
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From <strong>the</strong> previous discussion it is obvious that ytterbium acetate was rarely reported in<br />
organic chemistry. In our initial studies I tested different available Lewis acids with benzyl<br />
acetone as <strong>the</strong> ketone substrate. The original reported de was 80% using Ti (O i Pr) 4 / Ra-Ni, α-<br />
MBA, H 2 (120 psi), DCM. Benzyl acetone is an excellent substrate <strong>for</strong> screening as it is<br />
considerably cheap, available in large quantities with high purity from chemical suppliers and<br />
has high molecular weight facilitating its work up. Some <strong>of</strong> <strong>the</strong> tested Lewis acids and results<br />
obtained are summarized in (table 5.2).<br />
Table 5.2. a Different Lewis Acids Tested <strong>for</strong> <strong>the</strong> Reductive Amination <strong>of</strong> Benzyl Actone.<br />
Lewis Acid Ketone Left Alc. Formed Imine Left de%<br />
Dysprosium(III) acetate<br />
hydrate<br />
- - 1.36 77.5<br />
Lanthanum(III) acetate<br />
hydrate<br />
- - 1.3 76.44<br />
Lanthanum(III)<br />
trifluoromethanesulfonate<br />
90 - - NA<br />
Cerium<br />
trifluoromethanesulfonate<br />
90 - - NA<br />
Cerium(III) acetate<br />
hydrate<br />
1.6 - 1.29 76.9<br />
Indium(III) acetate 29.9 - 13.1 79.03<br />
Indium(III)<br />
trifluoromethanesulfonate<br />
90 - - NA<br />
104