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.
描述了一种在固体载体上合成N-未取代的
吡唑的新方法。固体支持物充当
氨基酸的保护基。N-保护的
氨基酸被N-亚硝化,随后在微波反应器中用
乙酸酐处理会产生中离子sydnones,它们在与
炔烃的1,3-偶极环加成反应中原位反应。产物的无痕裂解以高的总收率得到N-未取代的
吡唑。