Polymer-supported O-methylisourea: A new reagent for the O-methylation of carboxylic acids

Organic Letters

Volumn 4, Issue 6, 2002, Pages 1035-1037

  Crosignani, Stefano ^a   White, Peter D ^b   Linclau, Bruno ^a  

^a UNIVERSITY OF SOUTHAMPTON   (United Kingdom)

^b Novabiochem   (United Kingdom)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE;

EID: 0005120785     PISSN: 15237060     EISSN: None     Source Type: Journal    
DOI: 10.1021/ol025633s     Document Type: Article

References (13)

1. Otera, J. Angew. Chem., Int. Ed. 2001, 40, 2044-2045.
2. For a review on the use of O-alkyl isoureas see Mathias, L. J. Synthesis 1979, 561-76.
3. (a) Hugger, U.; Sharpless, K. B. Tetrahedron Lett. 1995, 36, 6603-6606.
4. (b) Biftu, T.; Acton, J. J.; Berger, G. D.; Bergstrom, J. D.; Dufresne, C.; Kurtz, M. M.; Marquis, R. W.; Parsons, W. H.; Rew, D. R.; Wilson, K. E. J. Med. Chem. 1994, 37, 421-424.
5. Rademann, J.; Smerdka, J.; Jung, G.; Grosche, P.; Schmid, D. Angew. Chem., Int. Ed. 2001, 40, 381-385.
6. Dains, F. B. J. Am. Chem. Soc. 1899, 21, 136-192.
7. (a) Lidstrom, P.; Tierney, J.; Wathey, B.; Westman, J. Tetrahedron 2001, 57, 9225-9283.
8. (b) Stadler, A.; Kappe, C. O. Eur. J. Org. Chem. 2001, 919-925.
9. N-Cyclohexylcarbodiimide-N′-methylpolystyrene HL 1 was provided by Novabiochem (loading 1.80 mmol/g). Alternatively, it can be prepared using the method described in Weinshenker, N. M.; Shen, C. M.; Wong, J. Y. Org. Synth. 1977, 56, 95-99.
10. The reaction is performed in a Smith Synthesizer, at a temperature of 135°C and a pressure of 9 bar.
11. The phenomenon has been attributed to a decreased solvent polarity at higher temperatures: Westman, J. Org. Lett, 2001, 3, 3745-3747.
12. Typical experimental procedure: carboxylic acid 3 (0.175 mmol) is dissolved in 2 mL of THF. The solution is added to resin 2 (200 mg, 0.35 mmol). The mixture is heated at 60°C with gentle stirring overnight; then the resin is filtered and washed with MeOH (3 × 2 mL) and DCM (3 × 3 mL). The solvent is then evaporated under reduced pressure to give the desired product.
13. Flynn, D. L.; Crich, J. Z.; Devraj, R. V.; Hockerman, S. L.; Parlow, J. J.; South, M. S.; Woodard, S. J. Am. Chem. Soc. 1997, 119, 4874-4881.