CuBr2.SMe2 (19.13 g, 93.1 mmol) was placed into a flame-dried flask along with THF (250 ml). The mixture was cooled to −78° C. and ethylmagnesium bromide (31 ml, 3.0 M in ether, 93.1 mmol) was added slowly. The reaction was stirred for 45 minutes under nitrogen. Boron trifluoride dimethyl etherate was added (11.7 ml, 93,1 mmol) and the mixture stirred for 5 minutes. Ethyl 1-(4-chlorophenylsulfonyl)-4-oxo-1,2,3,4-tetrahydropyridine-2-carboxylate (103; 8.0 g, 23.3 mmol) was added via syringe pump over a 2 hour period while maintaining −78° C. bath temperature. The reaction was stirred for 4 hours and quenched with a 1:1 solution of 2% NH4Cl/NH4OH. An equal amount of EtOAc and water was added and the mixture was filtered to remove solids. The layers were separated and the aqueous layer was extracted with two more portions of EtOAc. The organic layers were combined and dried over Na2SO4 and concentrated to yield a colorless oil (7.74 g). The material was purified by column chromatography using EtOAc/hexanes gradients to yield 5.84 g (67%) of a mixture of cis/trans (4:96) isomers.
