Lithium Chloride → (r)-5-Biphenyl-4-ylmethyl-3-[1-diisopropylamino-meth-(e)-ylidene]-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester

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Reaction Conditions

Reaction Steps

A mixture of potassium tert-butoxide (2.8 eq, 2.8 mmol, 1 M solution in THF) and N,N,N′N′-tetramethylformamidinium chloride (18, R6=Me, R7=Me) (3 eq, 3 mmol) are stirred at 60° C. for 1 h. The mixture is then cooled to room temperature. The mixture is then diluted with tetrahydrofuran to a total volume of 5 ml. (S)-2-Biphenyl-4-ylmethyl-5-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (8-a, R1=Boc) (1 eq, 1 mmol) and lithium chloride (1 eq, 1 mmol) is then added to the mixture. The mixture is then stirred at room temperature for 3 h. The volatiles are removed under reduced pressure. Ethyl acetate (20 ml) is added to the mixture. The phases are separated and the organic phase washed with saturated sodium carbonate solution (2×20 ml) and brine (20 ml). The organic phase is dried (Na2SO4) and concentrated under reduced pressure to afford (R)-5-biphenyl-4-ylmethyl-3-[1-dimethylaminometh-(E/Z)-ylidene]-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (7-a, R1=Boc, R6=Me, R7=Me) or a salt thereof. The solutions are analysed by TLC (50% ethyl acetate in hexane). RF 0.21 (salt of 7-a, R1=Boc, R6=Me, R7=Me); RF 0.27 (7-a, R1=Boc, R6=Me, R7=Me); RF 0.68 (8-a, R1=Boc).

Provenance & Evidence