C([Mg]Cl)(C)C.[N:6]1[C:11]2[S:12][C:13]([C:15]([O:17]C)=O)=[CH:14][C:10]=2[CH:9]=[N:8][CH:7]=1.[CH3:19][O:20][N-:21][CH3:22]>C1COCC1>[CH3:19][O:20][N:21]([CH3:22])[C:15]([C:13]1[S:12][C:11]2[N:6]=[CH:7][N:8]=[CH:9][C:10]=2[CH:14]=1)=[O:17]iPrMgCl (2M in THF, 1.1 mL) was added dropwise to a solution of methyl thieno[2,3-d]pyrimidine-6-carboxylate (intermediate 11) (138 mg) and N-methoxy-N-methylamide (104 mg) in THF at −20° C. maintaining the internal temperature below −5° C. The reaction was allowed to stir at −10° C. for 30 minutes and then quenched with NH4Cl (sat. aq). The solution was diluted with EtOAc and the organic layer was separated. The aqueous layer was extracted with EtOAc (2×15 mL) and then the combined organics dried (MgSO4), filtered and concentrated in vacuo. Purification by flash chromatography on silica eluting with hexane:EtOAc (1:1 to 1:4) afforded the title compound as a pale yellow solid (107 mg, 67%);
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