Abstract
A systematic study of chiral adducts derived from amines as catalysts for aldol reaction revealed that enantioselective outcome depends on the chiral enamine intermediate and not the face-selective activation of aldehyde. A simple addition compound of proline and 8-hydroxy quinoline was found to be a good catalyst.
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GRAPHICAL ABSTRACT
ACKNOWLEDGMENTS
Financial support for this work was provided by the National Chemical Laboratory (CSIR) through the “in-house” program. One of us (R.L.S.) thanks the Council of Scientific and Industrial Research, New Delhi, for a research scholarship. We are thankful to S. Kunte for chiral HPLC analysis.
Notes
a Isolated yield.
b Determined by HPLC analysis.
c Reaction was done at 25 °C.
a Acetone as the solvent.
b 10 mol% chiral amine achiral acid combination (1:1).
c Isolated yield.
d Determined by chiral HPLC analysis.
e Reported[ Citation 22 ]using 20 mol% of catalyst.
Note. A, benzoic acid; B, PTSA; C, salicylic acid; D, (±)-BINOL.
a Ten equivalents of donor reactant were used under neat conditions and two equivalents when a solvent was used.
b Isolated yield.
c Determined by chiral HPLC analysis.
d Reported[ Citation 3 ] using 30 mol % of proline.
e 3 vol% water in DMF.
Notes. A, 2-amino phenol; B, 8-hydroxy quinoline.
a Ten equivalents of donor reactant.
b Isolated yield.
c Determined by chiral HPLC analysis.
a Isolated yield.
b Determined by HPLC analysis.
c Determined by chiral HPLC analysis (major/ minor).