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A mixture of 28 g of 1,3-dimethoxybenzene and 24.3 g of TMEDA in 400 ml of hexane is cooled to a temperature below 10° C., 132 ml of a 1.6 M solution of n-butyllithium in hexane are added dropwise and the mixture is left stirring for 30 minutes. The reaction mixture is cooled to 0° C., 140 ml of diethyl oxalate are added over 15 minutes and the mixture is left stirring for 1 hour at RT. The reaction mixture is poured into a mixture of concentrated HCl solution and ice and is extracted with EtOAc, the organic phase is washed with water and dried over Na2SO4, and the solvent is evaporated off under vacuum. The excess diethyl oxalate is removed by distillation under vacuum (b.p.=90° C. at 2 400 Pa). The resulting crude product is chromatographed on silica gel, eluting with heptane and then with DCM. 34.5 g of the expected product are obtained.

1. additionare added dropwise
2. waitthe mixture is left
3. waitthe mixture is left
4. stirringstirring for 1 hour at RT
5. extractionis extracted with EtOAc
6. washthe organic phase is washed with water
7. dry with materialdried over Na2SO4
8. customthe solvent is evaporated off under vacuum
9. customThe excess diethyl oxalate is removed by distillation under vacuum (b.p.=90° C. at 2 400 Pa)
10. customThe resulting crude product is chromatographed on silica gel
11. washeluting with heptane