In this review an attempt has been made to compile all the existing comprehensive literature for the synthesis of 1,1-Dimethyl-3-oxobutyl-isothiocyanate (DMO-ITC) and its reactions with the compounds having different functional groups, such as amines, diamines, amino alcohols, amino phenols, amino thiophenols, amino nitriles, amino acids, and hydrazines. The peculiar behavior of the DMO-ITC is due to its sensitivity toward acids and gives different products when the reaction occurs in the absence and presence of an acid. The pH of the reaction condition also plays an important role. Normally, DMO-ITC gives pyrimidinethione derivatives when treated with amines, but reactions become interesting when the compounds have an amino group as well as the other functional group (NH 2 , OH, SH, CN, COOH) at ortho position, providing condensed bicyclic, tricyclic, or poly heterocycles with ring nitrogen and/or sulfur is of biological importance. The reaction of DMO-ITC with ethylene diamine, o -phenylenediamines, 1,2-diaminoanthraquinone, o -diaminonaphthalenes, N -aminoethyladenosine, 2-amino ethanol, o -aminophenols, o -aminothiophenols, o -aminobenzonitriles, and o -aminobenzoic acids gave imidazopyrimidinethione, pyrimidobenzimidazolethiones, pyrimidoanthraquinonimidazolethione, pyrimidonaphthoimidazolethiones, furanopurinimidazopyrimidinethione, oxazolopyrimidinethione, oxafluorenethiones, thiafluorenethiones, thioxophenanthreneones, and thiaphenanthreneones derivatives respectively. But similar reactions were not seen with o -diaminoheterocycles. Hydrazines derivatives gave seven-membered heterocycles, that is, triazepinethiones derivatives. The synthesis of the heterocycles are well defined in separate sections according to the update references.