3,4-dihydro-2H-pyran → methyl 1-(tetrahydro-2H-pyran-2-yl)-1H-benzimidazole-5-carboxylate

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Reaction Steps

A round-bottom flask was charged with 20 (1.76 g, 10 mmol), p-TsOH.H2O (38 mg, 0.2 mmol), 3,4-dihydro-2H-pyran (1.26 g, 15 mmol) and THF (20 mL). The reaction mixture was degassed with nitrogen and heated at reflux for 18 h, and then the solvent was removed under reduced pressure. The residue was diluted with DCM (250 mL) and water (50 mL). The organic layer was dried (MgSO4), filtered and concentrated in vacuo. The residue was purified by SiO2 chromatography eluting with a DCM/MeOH gradient (0.5 to 1.0% MeOH) to afford 2.5 g (90%) of methyl 1-(tetrahydro-2H-pyran-2-yl)-1H-benzo[d]imidazole-5-carboxylate (22) as a grey oil: MS (ESI) m/z=261.2 [M+1]+.

Provenance & Evidence