Bicarbonate Ion → HCID 22882072, compound

Participants

Reaction Steps

(3R*,4R*)-N,N-Diethyl-5-oxo-1-azabicyclo[2.2.2]octane-3-carboxamide (180 g, 0.804 mol) and (-)-dibenzoyl-L-tartaric acid (L-DBT) monohydrate (211 g, 0.561 mol) were added to ethanol (3.65 L), and the resultant mixture was heated at reflux until a clear solution was obtained. The solution was rapidly cooled down to c.a. 40° C. in a water-bath, and allowed to stand overnight to form crystals, which were collected by filtration. The obtained crystals (100.5 g, 21.5%) were found to be (+)-(3R,4R)-N,N-diethyl-5-oxo-1-azabicyclo[2.2.2]-octane-3-carboxamide L-DBT salt with 97% optical purity. An additional amount of (-)-L-DBT monohydrate (90.6 g, 0.241 mol) was added to the mother liquor, which was concentrated to c.a. 3.5 L by evaporation. The resulting mixture was heated at reflux to give a clear solution, which was allowed to stand at room temperature. After 2 days, formed crystals were collected by filtration. The crystals (117 g, 25%) were found to be (-)-(3S,4S)-N,N-diethyl-5-oxo-1-azabicyclo[2.2.2]-octane-3-carboxamide L-DBT salt with 92% optical purity. The same resolution process was repeated starting from 220 g of (3R*,4R*)-N,N-diethyl-5-oxo-1-azabicyclo[2.2.2]-octane-3-carboxamide. From this run, the L-DBT salt of the (+) enantiomer (180 g, 31%) with 95% optical purity and the L-DBT salt of the (-) enantiomer (91 g, 16%) with 97% optical purity were obtained. The L-DBT salt of the (-) enantiomer from the above two runs were combined, and suspended in 1.5 l of ethanol. The resulting suspension was heated at reflux for 3 hours, and allowed to stand overnight at room temperature. The obtained crystals were converted to the free amine by base treatment (aqueous bicarbonate) followed by extraction with methylene chloride to afford (-)-(3S,4S)-N,N-diethyl-5-oxo-1-azabicyclo[2.2.2]-octane-3-carboxamide (73 g, 18%) having greater than 99% optical purity. Similarly, 83 g of of the (+) enantiomer (21%) was obtained with greater than 99% optical purity. The above mentioned optical purities were determined using a chiral HPLC. The absolute configuration was determined by X-ray crystallography of the dibenzoyl-L-tartaric acid salt of the (-) enantiomer.

Provenance & Evidence