Reaction #162296

Reaction equation

azepan-2-one

trimethyloxonium tetrafluoroborate

→

(E)-7-methoxy-3,4,5,6-tetrahydro-2H-azepine

Yield 95.0%

Solvents

DCM

Conditions

Workup

1. 1
   OtherThe reaction was quenched by the addition of saturated aqueous NaHCO3 (5 ml) (caution: vigorous CO2 evolution)
2. 2
   workup.ADDITIONMore aqueous sodium hydrogen carbonate was added until the aqueous layer
3. 3
   OtherThe organic layer was removed
4. 4
   Extractionthe aqueous layer extracted with DCM (5 mL)
5. 5
   DryingCombined organic layers were dried over anhydrous sodium sulfate
6. 6
   Filtrationfiltered
7. 7
   Otherevaporated under reduced pressure

Procedure

To a solution of azepan-2-one (1.13 g, 10.0 mmol) in DCM (10 mL) in a 40 mL screw cap vial was added freshly prepared trimethyloxonium tetrafluoroborate (1.57 g, 10.59 mmol). The resulting suspension was shaken overnight. The reaction was quenched by the addition of saturated aqueous NaHCO3 (5 ml) (caution: vigorous CO2 evolution). More aqueous sodium hydrogen carbonate was added until the aqueous layer reached pH 8. The organic layer was removed and the aqueous layer extracted with DCM (5 mL). Combined organic layers were dried over anhydrous sodium sulfate, filtered and evaporated under reduced pressure to yield (E)-7-methoxy-3,4,5,6-tetrahydro-2H-azepine (1.2 g, 95%) as a clear oil. LCMS (+ESI) m/z 128.2 [M+H]+. 1H-NMR (CDCl3) δ 3.60 (s, 3H), 3.45 (m, 2H), 2.40 (m, 2H), 1.80 (m, 2H), 1.60-1.50 (m, 4H).

Source