Diisopropylamine → 1-Methyl-3-(2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentyl)-4-phenyl-2-azetidinone

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Reaction Steps

10 mmoles of n-butyllithium (6.67 ml of a 1.5 molar solution in hexane) was added to a stirred solution containing diisopropylamine (1.40 ml; 10 mmoles) and 25 ml of diethyl ether at -70° C. This reaction mixture was stirred for 10 min and then 2,2,5,5-tetramethyl-1-aza-2,5-disilacyclopentane-1-acetic acid ethyl ester (2.45 g; 10 mmoles) was added. The solution was stirred for another 15 min at -70° C. and then 10 mmoles of zinc dichloride (6.76 ml of a 1.48 molar solution in diethylether) was added. After 5 min at -70° C., a white solid (LiCl) began to precipitate. Then N-(benzylidene)methylamine (1.19 g; 10 mmoles) was added. The reaction mixture was stirred for another 15 min at -70° C. and, after being warmed up to room temperature, quenched with 20 ml of a saturated aqueous ammonium chloride solution. The water layer was extracted with diethyl ether. The diethyl ether extract was washed with water, dried with sodium sulfate and concentrated in vacuo to give 3.05 g (96%) of the pure 2-azetidinone product as a pale yellow solid. The 1H NMR spectrum revealed that the product was a mixture of cis and trans isomers (cis/trans ratio 8:92).

Provenance & Evidence