4-Chloro-7-nitrobenzofurazan (NBD-Cl) is a highly sensitive chromogenic and fluorogenic reagent. It is reported to react spontaneously with trans-1-methoxy-3-(trimethylsilyloxy)-1,3-butadiene (Danishefsky′s diene), to afford regioselectively the silyl enol ether, via normal electron-demand Diels-Alder (NEDDA) reaction. A study of the molecular structure, vibrational spectra and NBO (Natural Bond Orbital) analysis of NBD–Cl has been undertaken. Its utility as a pre-column derivatization agent has been examined.