Solid-phase synthesis of amino acid derived N-unsubstituted pyrazoles via sydnones.
A new method to synthesize N-unsubstituted pyrazoles on a solid support is described. The solid support acts as a protecting group for the amino acid. N-Protected amino acid is N-nitrosated, and the subsequent treatment with acetic anhydride in a microwave reactor yields mesoionic sydnones that react in situ in 1,3-dipolar cycloaddition reactions with alkynes. Traceless cleavage of the products gives N-unsubstituted pyrazoles in high overall yields.
Harju
Kirsi
K
Division of Pharmaceutical Chemistry, Faculty of Pharmacy, P.O. Box 56, FI-00014 University of Helsinki, Finland.
Vesterinen
Johanna
J
Yli-Kauhaluoma
Jari
J
D000480:Alkynes / Q000737:chemistry; D000596:Amino Acids / Q000737:chemistry*; D002384:Catalysis; D015394:Molecular Structure; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000737:chemistry; D013558:Sydnones / Q000737:chemistry*
D000480:Alkynes; D000596:Amino Acids; D011720:Pyrazoles; D013558:Sydnones