Reaction #431956

Reaction equation

sulpholane

ammonium persulphate

2-chloro-1,4-naphthoquinone

4-methoxycyclohexane-1-carboxylic acid

→

2-chloro-3-(4-methoxycyclohexyl)-1,4-naphthoquinone

Solvents

acetonitrile

water

water

Conditions

Workup

1. 1
   workup.ADDITIONwas added dropwise during 15 minutes
2. 2
   Temperaturecooled in ice
3. 3
   Extractionextracted with ether
4. 4
   WashThe ether extracts were washed with sodium bicarbonate solution
5. 5
   Otherdried
6. 6
   Otherevaporated
7. 7
   OtherThe crude product was recrystallised from acetonitrile

Procedure

A mixture of 2-chloro-1,4-naphthoquinone (1.16 g), 4-methoxycyclohexane-1-carboxylic acid (1.3 g) and silver nitrate (0.3 g) were stirred at 65° C. in a mixture of acetonitrile (2.5 ml), sulpholane (7.5 ml) and water (17.5 ml) while a solution of ammonium persulphate (2.3 g) in water (5 ml) was added dropwise during 15 minutes. The reaction mixture was stirred for a further 15 minutes at 65° C., cooled in ice and extracted with ether. The ether extracts were washed with sodium bicarbonate solution, dried and evaporated. The crude product was recrystallised from acetonitrile to yield 2-chloro-3-(4-methoxycyclohexyl)-1,4-naphthoquinone, m.p. 110°-113° C.; the product so obtained (0.9 g) was dissolved in boiling methanol (25 ml) and a solution of potassium hydroxide (0.9 g) in water (9 ml) added dropwise during 10 minutes. The reaction mixture was then refluxed for a further 30 minutes, concentrated hydrochloric acid (5 ml) added dropwise and the mixture cooled in ice. Addition of an equal volume of water precipitated an oil which slowly turned to a semi-solid. Recrystallisation from acetonitrile yielded 2-hydroxy-3-(4-methoxycyclohexyl)-1,4-naphthoquinone, m.p. 152°-155°, shown by n.m.r. to be the pure trans isomer.

Source