Hexamethylenetetramine → 3-Methylnaphthalene-2-carbaldehyde

2,3-Dimethylnaphthalene (20.0 g), N-bromosuccinimide (22.8 g) and benzoyl peroxide (0.2 g) were refluxed in carbon tetrachloride (160 ml) for 12 hr. After cooling, the mixture was filtered. The filtrate was evaporated under reduced pressure and the residue was dissolved in chloroform. This solution was added dropwise to a vigorously stirred solution of hexamethylenetetramine (1.2 equiv) in chloroform (100 ml) and the mixture was heated at reflux for 12 hr. After cooling the salt was filtered off and was washed with several portions of hexane. The dried salt was heated at reflux with a 50% aqueous acetic acid solution (20 ml/g) for 2 hr. Concentrated hydrochloric acid (2 ml/g) was added and the mixture was heated at reflux for a further 15 min. The solution was poured onto ice-water and the resulting mixture was extracted with ether. The dried (MgSO4) organic fraction was evaporated and the residue was purified by recrystallization (twice) from hexane to give 3-methylnaphthalene-2-carboxaldehyde as cream-coloured clusters, mp 119° C. Pmr spectrum (CDCl3 ; δ in ppm): 2.75 (3H,s); 7.32-7.98 (5H,m); 8.24 (1H,s); 10.27 (1H,s). 6-Methylnaphthalene-2-carboxaldehyde was similarly prepared from 2,6-dimethylnaphthalene and was obtained as a white solid, mp 120° C. Pmr spectrum (CDCl3; δ in ppm): 2.58 (3H,s); 7.38-8.07 (5H,m); 8.30 (1H,s); 10.14 (1H,s).

1. temperatureAfter cooling
2. filtrationthe mixture was filtered
3. customThe filtrate was evaporated under reduced pressure
4. dissolutionthe residue was dissolved in chloroform
5. temperaturethe mixture was heated
6. temperatureat reflux for 12 hr
7. temperatureAfter cooling the salt
8. filtrationwas filtered off
9. washwas washed with several portions of hexane
10. temperatureThe dried salt was heated
11. temperatureat reflux with a 50% aqueous acetic acid solution (20 ml/g) for 2 hr
12. additionConcentrated hydrochloric acid (2 ml/g) was added
13. temperaturethe mixture was heated
14. temperatureat reflux for a further 15 min
15. additionThe solution was poured onto ice-water
16. extractionthe resulting mixture was extracted with ether
17. dry with materialThe dried (MgSO4) organic fraction
18. customwas evaporated
19. customthe residue was purified by recrystallization (twice) from hexane

ORD record

ord-0f566dd03dd64a2fa40939cc68341faa

Source dataset

uspto-grants-1987_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US04640708