SYNTHESIS OF 9-BROMOTRIPTYCENE

• Place 2.3g (0.02 mol) of isopentyl nitrite (isoamyl nitrite), 2.6g (0.01 mol) of 9-bromoanthracene and 25 ml of 1,2-dimethoxyethane ('glyme')  in a 250-ml round-bottomed flask fitted with a reflux condenser. 

• Heat the mixture to gentle reflux on an electric mantle and add down the condenser, dropwise during 30 minutes, a solution of 3.4g (0.025 mol) of anthranilic acid in 15 ml of glyme. 

• Remove the mantle, cool the mixture to about 40 °C and add 2.3g more of isopentyl nitrite dissolved in 5 ml of glyme. 

• Resume the gentle refluxing and add during 15 minutes another solution of 3.4g of anthranilic acid in 10 ml of glyme. 

• Heat for an additional 15 minutes, add 1 ml of 95 per cent ethanol and pour the reaction mixture into a solution of 3.0g of sodium hydroxide in 100 ml of water. 

• Cool the resulting brown suspension thoroughly in ice-water and filter under suction. 

• Wash the residue with a chilled methanol/water mixture (4 : 1 v/v) and transfer to a 100-ml round-bottomed flask which is then evacuated (rotary evaporator) on a steam bath until the weight is constant. 

• To the flask containing the crude product, add 2.0g (0.02 mol) of maleic anhydride and 25 ml of triethyleneglycol dimethyl ether ('triglyme', b.p. 222 °C), fit a reflux condenser and boil under reflux for 10 minutes over a Bunsen flame. 

• Cool the solution to about 100 °C, add 10 ml of 95 per cent ethanol and pour into a solution of 3.0g of sodium hydroxide in 75 ml of water. 

• Stir for a few minutes, then cool in ice-water and filter under suction. 

• Wash the residue with chilled methanol/water (4 : 1 v/v) and recrystallise from methylcyclohexane or a chloroform/methanol mixture to give colourless plates of 9-bromotriptycene, m.p. 251-256 °C; yield is 1.5g (45%). 

• Further recrystallisation gives the pure product, m.p. 258-262 °C.