A robust, chemoselective direct condensation/cyclization of thioureas and amino alcohols is described. Employing a bench-stable Vilsmeier reagent, methoxymethylene-N,N-dimethyliminium methyl sulfate, the selective in situ activation of alcohols is achieved with high efficiency and broad functional-group tolerance. The reversible interaction of the Vilsmeier reagent with substrate was key to the success of this activation strategy.