Reaction #2320129

Reaction equation

paraformaldehyde

paraformaldehyde

N-methylanilinium trifluoroacetate

diethyl ether

α-tetralone

→

2-methylene-3,4-dihydronaphthalen-1-one

Yield 92.4%

Solvents

THF

Conditions

Workup

1. 1
   TemperatureThe solution was heated
2. 2
   Temperatureat reflux under nitrogen
3. 3
   workup.DISSOLUTIONdissolved
4. 4
   TemperatureAfter cooling
5. 5
   OtherThe solvent was separated from the reaction mixture
6. 6
   Washwashed with 500 mL of saturated sodium bicarbonate
7. 7
   workup.ADDITIONAdditional diethyl ether was added to the reaction mixture
8. 8
   Otherseparated
9. 9
   Extractionto back extract the aqueous sodium bicarbonate layer
10. 10
    DryingThe combined organic layers were dried over magnesium sulfate
11. 11
    Concentrationthe solution was then concentrated to a volume of approximately 300 mL
12. 12
    Filtrationfiltered through Celite
13. 13
    OtherComplete evaporation of the ether

Procedure

To a suspension of paraformaldehyde (46.2 g, 1.54 mol) and N-methylanilinium trifluoroacetate (TAMA, 46.2 g, 1.54 mol) in 340 mL of dry THF was added α-tetralone (50 g, 0.342 mol). The solution was heated at reflux under nitrogen with stirring for 4 h, during which time the paraformaldehyde dissolved. After cooling, diethyl ether (700 mL) was added to the reaction mixture. The solvent was separated from the reaction mixture and washed with 500 mL of saturated sodium bicarbonate. Additional diethyl ether was added to the reaction mixture, separated and used to back extract the aqueous sodium bicarbonate layer. The combined organic layers were dried over magnesium sulfate, and the solution was then concentrated to a volume of approximately 300 mL and filtered through Celite. Complete evaporation of the ether yielded 50 g (90%) of crude 2-methylene-3,4-dihydronaphthalen-1-one, which was used immediately for the next reaction to prevent polymerization of the product.

Source