Facile reaction of thiols and amines with alkyl 4-hydroxy-2-alkynoates in water under neutral conditions and ultrasound irradiation

This Letter describes an alternative protocol for the Michael addition of thiols to 4-hydroxy-2-alkynoates. The reaction proceeds at room temperature in water under ultrasound irradiation. With amines instead of thiols a sequential conjugate addition/lactonization reaction leads to important 4-amino-furan-2-one derivatives.