Reaction #6629

Reaction equation

phenyl-3-methylbut-2-enylsulfide

Compound 60

phenyl-3-methylbut-2-enylsulfide

phosphorus pentoxide

phosphoric acid

benzene

→

title compound

4,4-Dimethylthiochroman

Conditions

Workup

1. 1
   TemperatureThis solution was refluxed
2. 2
   OtherThe supernatant organic layer was decanted
3. 3
   Extractionthe syrupy residue extracted with 3×50ml ether
4. 4
   Washwashed with water, saturated NaHCO3 and saturated NaCl solutions
5. 5
   Dryingdried (MgSO4)
6. 6
   OtherSolvent was removed in vacuo
7. 7
   workup.DISTILLATIONthe residue purified by kugelrohr distillation (80 degrees C., 0.5mm)

Procedure

To a solution of 15.48g (86.824 mmol) of phenyl-3-methylbut-2-enylsulfide (Compound 60) in 160ml benzene were added successively 12.6g (88.767mmol) of phosphorus pentoxide and 11 ml of 85% phosphoric acid. This solution was refluxed with vigorous stirring under argon for 20 hours, then cooled to room temperature. The supernatant organic layer was decanted and the syrupy residue extracted with 3×50ml ether. Organic fractions were combined and washed with water, saturated NaHCO3 and saturated NaCl solutions and then dried (MgSO4). Solvent was removed in vacuo and the residue purified by kugelrohr distillation (80 degrees C., 0.5mm) to give the title compound as a pale yellow oil. PMR (CDCl3) :& 1.30 (6H, s), 1.90-1.95 (2H, m), 2.95-3.00 (2H, m), 6.96-7.00 (2H, m), 7.04-7.07 (1H, m), 7.30-7.33 (1H, m).

Source