To a 1 M solution of o-tolylmagnesium chloride in THF (6.26 ml, 41.5 mmol) was added dropwise a freshly prepared solution of dried zinc chloride (8.48 g, 62.2 mmol) in dry THF (200 ml) at 0° C. After completed addition the reaction mixture was allowed to slowly warm to room temperature over a period of 1 h. To this mixture were added a solution of 4-trifluoromethanesulfonyloxy-5,6-dihydro-2H-pyridine-1,3-dicarboxylic acid 1-tert-butyl ester 3-methyl ester (10.7 g, 27.5 mmol) in THF (270 ml) and tetrakis(triphenylphosphine)palladium(0) (0.96 g, 0.83 mmol). After stirring for 6 h at room temperature the reaction was quenched with ice. The mixture was diluted with tert-butyl methyl ether and washed with 2 M aqueous sodium carbonate solution. The aqueous layer was extracted with two portions of tert-butyl methyl ether.
