The reaction of imidazo [2, 1-b] thiazolines with various organometallic reagents is described. Nucleophilic attack of organolithium reagents on sulfur occurs with extrusion of ethylene to produce 2-thioalkyl-or 2-thioarylimidazoles. The outcome with Grignard reagents, however, is less predictable, with some reagents adding at sulfur and others reacting at C-2 or not at all.