Process for producing 3-thia substituted alkane 1,4 diones comprising the steps of:I. Providing a 2-ene-1,4 dione having the structure: ##SPC1##Ii. Intimately admixing said 2-ene-1,4 dione with a sulfur compound having the formula:R.sub.3 SH thereby providing a substituted or sunsubstituted 2-thia substituted alkane 1,4 dione having the structure: ##SPC2##WhereinR.sub.3 is selected from the group consisting of acyl and royl, wherein R.sub.2 is lower alkyl; and wherein R.sub.1, R.sub.4 and r.sub.6 are the same or different and are selected from the group consisting of hydrogen and lower alkyl; wherein when R.sub.1 is hydrogen, the reaction (ii) is carried out in the presence of an organic base; and wherein when R.sub.1 is lower alkyl, the reaction (ii) is carried out in the absence of catalyst. Examples of such organic bases are piperidine, pyridine, triethyl amine, quinoline or alpha-picoline.