0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest. Please login or sign up for a free trial to access the full content. Variation 2: Heterogeneous Catalytic Asymmetric Hydrogenation of 2-Oxoalkanoates

DOI: 10.1055/sos-SD-020-01122

Chemler, S. R.; Zabawa, T. P.Science of Synthesis, (2007201216.

The enantioselective hydrogenation of alkyl 2-oxoalkanoates with a heterogeneous cinchona-modified platinum/alumina catalyst system is known as the Orito reaction.[‌102‌‌104‌] Heterogeneous catalysts offer the benefit of catalyst recovery from the reaction medium by a simple filtration procedure. Several cinchona modifiers are shown in Scheme 14. Reduction of α-oxo esters using the cinchonidines 35 provides the (R)-α-hydroxy ester while the cinchonines 36 provide the (S)-α-hydroxy ester.

Meeeee 88 Meeeeeee Meeeeeee Meeeeeeee[‌888‌‌888‌]

Meeeeeeeeee 88

Meeeeeee Meee Meeeeeeeeeee Meeeee
Meeeeeeee M8 M8
88 M MM=MM8 eeeeeeeeeeee MM 8M,8M
88 M Me eeeeeeeeeeeeeeeeeee MMMM 8M,8M
88 Me Me (8M)-8-eeeeeee-88,88-eeeeeeeeeeeeeeeeeee MeMMMM 8M,8M
88 M MM=MM8 eeeeeeeeee MM 8M,8M

α-Meeee- eee α-eeee-eeeeeeeeeee α-eee eeeeee 88 eee eeee eeeeeeeeee eee eee Meeee eeeeeeee eeeeee eee α-eeeeeee eeeee 88 eeee eeeeeeeeeeeeeeeeeeee ee >88% (Meeeee 88).[‌888‌‌888‌] Meee eeeeeeee eee eeee ee eeee eee eee eeeeeeeeeeeeeeee eeeeeeeee ee 8-eeeeeeeeeeeeeee eeee ee eeeee (88% ee).[‌888‌]

Meeeee 88 Meeeeeeeeeeeeeee Meeeeeeeeeeee ee α-Mee Meeeee eeee Meeeeeee-Meeeeeee Meeeeeee/Meeeeee Meeeeeee[‌888‌‌888‌]

Meeeeeeeeee 88

M8 Meeeeeee Meeeeee M8 (eee) Meee (°M) Meeeee ee (%) Mee
Me 88 (M8=M; M8=MM=MM8) MeMM 88 88 M 88 [‌888‌]
eMe 88 (M8=M; M8=Me) MeMM, eeeeeee 88 8 M 88 [‌888‌]
Me 88 (M8=M; M8=Me) MeMM, eeeeeee 88 8 M 88 [‌888‌]
(MM8)8Me 88 (M8=M; M8=Me) MeMM, eeeeeee 8.8 88 M 88 [‌888‌]
(MM8)8MM8Me 88 (M8=M; M8=Me) MeMM 8 88 M 88 [‌888‌]