18-Crown-6 → (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 Steps

(S)-2-Biphenyl-4-ylmethyl-5-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (8-a, R1=Boc) (2 mmol) is added to potassium hexafluorophosphate (1 eq) and 18-crown-6 (1 eq). Bredereck's reagent [Tris(dimethylamino)methane (13, R6=Me, R7=Me), Tert-Butoxy-bis(dimethylamino)methane (14, R6=Me, R7=Me, R8=tBu) and N,N-Dimethylformamide di-tert-butyl acetal (15, R6=Me, R7=Me, R8=tBu)] (4 ml) is added. The mixture is then stirred at ambient temperature for 3 h 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