3,4-dihydro-2H-pyran → Indole

Participants

Reaction Steps

3,4-Dihydro-2H-pyran (3.9 ml, 42.7 mmol) was added to a stirred solution of 4-(1,2,4-triazol-1-ylmethyl)phenylhydrazine (EP 497,512; 4.0 g, 21.1 mmol) in dioxane/water/5N HCl (38 ml/14 ml/4.7 ml) and stirred at room temperature for 1.75 h. The solution was then refluxed for 1.5 h and the solvent removed under vacuum. The residue was taken up into CH2Cl2 and saturated aqueous K2CO3 solution. The aqueous was separated and further extracted with CH2Cl2 (×4). The combined organic extracts were dried (MgSO4) and evaporated and the residue chromatographed on silica gel eluting with CH2Cl2 /MeOH/NH3 (80:8:1) to give the title-indole (0.919 g, 17%), δ(250 MHz, CDCl3) 1.91-2.03 (2H, m, CH2), 2.84 (2H, t, J=7.9 Hz, CH2), 3.73 (2H, t, J=7.9 Hz, CH2), 5.43 (2H, s, CH2), 7.04 (1H, d, J=2.3 Hz, Ar--H), 7.11 (1H, dd, J=2.3 and 8.3 Hz, Ar--H), 7.35 (1H, d, J=8.3 Hz, Ar--H), 7.58 (1H, s, Ar--H). 7.97 (1H, s, Ar--H). 8.02 (1H, s, Ar--H), 8.18 (1H, s, NH).

Provenance & Evidence