A new method for introduction of indolylmethyl group to aldehydes or ketones using diethyl (o-isocyanophenylmethyl)phosphonate through Horner-Wadsworth-Emmons condensation, thiol-mediated radical cyclization, and the subsequent desulfurization is described. The Horner-Wadsworth-Emmons reagent was prepared from 2-nitrobenzaldehyde in a concise three-step sequence.