Synthesis of 2H-Chromenes in Ionic Liquid Solvents

Abstract

Vinylboronic acids react with o-hydroxyaryl aldehydes in room temperature ionic liquids in the presence of secondary amines to generate 2H-chromenes.

Key Words

ionic liquid - chromenes - Petasis reaction - boronic acid - green chemistry

References

• 1a Welton T. Chem. Rev.  1999,  99:  2071 
• 1b Sheldon R. Chem. Commun.  2001,  2399 
• 2 Freemantle M. Chem. Eng. News  2000,  78:  37 
• 3a Laali KK. Gettwert VJ. J. Org. Chem.  2001,  66:  35 
• 3b Park S. Kazalauskas R. J. Org. Chem.  2001,  66:  8395 
• 3c Brown RA. Pollet P. McKoon E. Eckert CA. Liotta CL. Jessop PG. J. Am. Chem. Soc.  2001,  123:  1254 
• 3d Carmichael AJ. Earle MJ. Holbrey JD. McCormac PB. Seddon KR. Org. Lett.  1999,  1:  997 
• 4a Sengchantara ST. Wallace TW. Nat. Prod. Rep.  1986,  3:  465 
• 4b Nicolaou KC. Pfefferkorn JA. Cao G.-Q. Angew. Chem. Int. Ed.  2000,  39:  734 
• 4c Varma RS. Kabalka GW. Heterocycles  1985,  23:  139 
• 5a Petasis NA. Akritopoulou I. Tetrahedron Lett.  1993,  34:  583 
• 5b Petasis NA. Zavialov IA. J. Am. Chem. Soc.  1997,  119:  445 
• 5c Petasis NA. Zavialov IA. J. Am. Chem. Soc.  1998,  120:  11798 
• 5d Kabalka GW. Venkataiah B. Dong G. Tetrahedron Lett.  2004,  45:  729 
• 6 Wang Q. Finn MG. Org. Lett.  2000,  2:  4063 
• 7 Kabalka GW. Malladi RR. Chem. Commun.  2000,  2191 

8

After extracting the product from the ionic liquid, the ionic liquid was diluted with acetone; a white solid precipitated and was removed by filtration. The acetone was evaporated under reduced pressure, and the ionic liquid was then reused.