1,1-Dibromoethane → 5-Methyl-1,4-benzodioxane

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Reaction Steps

Dry potassium carbonate (0.93 eq.) is added to a solution of ortho-methylcatechol (10 g) dissolved in 150 ml of acetone under an argon atmosphere; the reaction mixture is heated to a gentle reflux and dibromoethane (0.4 eq.) is then added. Those operations are repeated twice at 15 minute intervals and in identical proportions (that is to say, in total 2.8 eq. of K2CO3 and 1.2 eq. of dibromoethane are added). After 12 hours' reflux, the latter is again introduced into the reaction mixture in an altogether identical amount (that is, 1.2 eq.). Heating is continued for 72 hours. The solution obtained is cooled, the salts are then filtered off over Celite and the filtrate is concentrated, hydrolysed with 60 ml of water and then extracted with dichloromethane. The recovered organic phase is washed with a 5% sodium hydroxide solution, dried over magnesium sulphate and evaporated. The cyclised product is purified over a flash silica column eluted with a 2:8 AcOEt/PE mixture (PE=petroleum ether). Yellow oil.

Provenance & Evidence