Bicyclic Ketol

Hajos–Parrish–Eder–Sauer–Wiechert Reaction
... reaction equation - leading to the optically active bicyclic ketol as well as the Eder-Sauer-Wiechert modification leading to the optically active enedione through the loss of water from the ketol ... and it requires just 3% of proline to obtain the reaction product, a ketol in 93% enantiomeric excess ... enabling them to isolate the optically active intermediate bicyclic ketol ...

Hajos–Parrish–Eder–Sauer–Wiechert Reaction - Reaction Mechanism
... be followed by ring closure to the above shown optically active bicyclic ketol product (see Figure 1.) under the influence of the catalytic amount of (S)-(-)-proline ... gave the expected optically active bicyclic ketol (+)-(3aS,7aS)-3a,4,7,7a-tetrahydro-3a-hydroxy-7a-methyl-1,5(6H)-indanedione with (S)-(-)-proline catalyst ... to give the (-)-(3aR,7aR)-3a,4,7,7a-tetrahydro-3a-hydroxy-7a-methyl-1,5(6H)-indanedione bicyclic ketol enantiomer identical to the one obtained with unnatural (R)-(+)-proline ...