Potassium tert-butoxide → (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

A 1 M solution of potassium tert-butoxide in THF (11.7 ml) is added to diisopropyl(piperidin-1-ylmethylidene)ammonium hexafluorophosphate (5 g, prepared according to Example 12). The resulting mixture is then stirred for 1 h at 50° C. (S)-2-Biphenyl-4-ylmethyl-5-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (8-a, R1=Boc) (1 g) is then added to the reaction and the resulting mixture is stirred for 1 h at room temperature. The mixture is diluted with isopropyl acetate and filtered through silica. The residue is concentrated in vacuo then purified by column chromatography (ethyl acetate) to give (R)-5-biphenyl-4-ylmethyl-3-[1-diisopropylamino-meth-(E)-ylidene]-2-oxo-pyrrolidine-1-carboxylic acid tert-butyl ester (7-a, R1=Boc, R6=iPr, R7=iPr). Rf 0.55 (ethyl acetate). 1H NMR (DMSO-d6), 7.65-7.62 (2H), 7.61-7.58 (2H), 7.47-7.42 (2H), 7.37-7.31 (1H), 7.29-7.25 (2H), 7.01 (1H), 4.28-4.20 (1H), 3.84-3.70 (2H), 3.07-3.01 (1H), 2.82-2.73 (1H), 2.71-2.63 (1H) 2.49-2.44 (1H), 1.49 (9H), 1.13-1.08 (12H).

Provenance & Evidence