Selective monoethynylation of isatins using solid calcium carbide as a surrogate of gaseous acetylene

Abstract

Highly selective monoethynylation of isatins using solid calcium carbide as a surrogate of gaseous acetylene was described. A series of multifunctional compounds, 3-ethynyl-3-hydroxyindolin-2-ones, were efficiently synthesized at room temperature through a one-step procedure. The salient features of this protocol are the use of inexpensive and easy-to-handle solid alkyne sources instead of inflammable and explosive acetylene gas, the use of commercially available substrates, mild reaction conditions, and simple workup procedures.