Benzene → HCID 21439127, compound

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Reaction Steps

2.78 G. of 2-(5-oxo-5H-dibenzo[a,d]cyclohepten-2-yl)propionic acid is stirred in a mixture of 20 ml. of benzene and 5 ml. of trifluoroacetic anhydride for 15 minutes. The mixture is evaporated to dryness and redissolved in 20 ml. of dry benzene. A mixture of 1.0 g. of pyridine and 2.44 g. (2 moles) of (+) α-phenylethanol is added. The mixture is left for 30 minutes and then water and ether is added. The organic layer is washed with dilute hydrochloric acid and water, then dried and evaporated. The residue is chromatographed on 100 g. silica gel, eluting with hexane:ether (4:1) to afford a 1:1 mixture of diastereomeric esters. Repeated crystallization of this mixture from ether-hexane yields the less soluble isomers. The purity of samples from successive recrystallizations is monitored by gas-liquid chromatography using a 1 meter × 2 mm. column packed with Chromosorb W (Regis Chemical Co., Chicago, Ill.) impregnated with 3% w/w OV101 polymeric material (Applied Sciences Laboratory, Inc., State College, Penn.) as stationary phase, and helium as the carrier gas at 220°C. The less soluble isomer is decomposed by stirring in a mixture of 5 ml. of benzene and 5 ml. of trifluoroacetic acid for 30 minutes. Water and ether are added and the ethereal layer washed with water, and then with dilute aqueous sodium carbonate. The aqueous layer is acidified with dilute hydrochloric acid and then extracted with ether. The ethereal layer is washed, dried and evaporated to give d 3-(5-oxo-5H-dibenzo[a,d]cyclohepten-2-yl)propionic acid. 1 2-(5-Oxo-5H-dibenzo[a,d]cyclohepten-2yl)propionic acid [m.p. 105°-107°C; [α]D -47.4° (chloroform)] can be obtained in similar manner using (-) α-phenylethanol.

Provenance & Evidence