(S)-mandelic acid → (2s)-Cyclohexyl(hydroxy)acetic acid

Participants

Reaction Steps

(S)(+)-Mandelic acid (76.0 g) was dissolved in 440 ml methanol containing 5 ml glacial acetic acid. The phenyl ring was entirely reduced in the presence of 5 gm. of 5% rhodium-on-alumina catalyst under 100 psi H2 pressure in 10 hrs. Following filtration of the solution through Celite® (diatomaceous earth) to remove the catalyst, the methanol was removed via a rotary evaporator. The resulting white solid was dissolved in 1 liter (l) of hot diethyl ether and filtered while hot. The volume of the solution was reduced to 400 ml and 250 ml cyclohexane was added. The ether was then removed and the resultant cyclohexane solution was stored several hours under refrigeration. White crystals of the desired product formed and were collected via filtration. The solid was dried overnight in vacuo at 40° C. Seventy-one grams of (S)(+)-hexahydromandelic acid were obtained for a 90% yield: m.p. 128°-129° C. (lit., 129° C.) and [α]D23 =+23.5° (1, HOAc) (lit. [α]D23 =+25.5 (1.1, HOAc) for the (R) (+) isomer.

Provenance & Evidence