Synthesis of 1,1,2-trifluoro-4-(substituted sufonyl)-but-1-ene

A process for preparing a compound of formula [I], the process comprises:

• (a) reacting a compound of formula [II] with an oxidizing agent and a catalyst, wherein the process is carried out at a temperature of about −5° C.-25° C.
• wherein, R1 is an optionally substituted heterocyclic aromatic ring, wherein the catalyst is selected from the group consisting of TaCl5, Ta(OEt)5, NbCl5, Nb2O5, TiO2/H3PO4, Ti(OiPr)4, V2O3, V2O5, VO(acac)2, Na2WO4, WO2, WO3, WO, WF6, wrought tungsten and two tungsten-copper pseudoalloys, W metal, W metal in combination with Al2O3, WF6, mixed oxo-flurocomplexes of W(VI), WO5·HMPT·H2O wherein HMPT is hexamethyl phosophoric acid triamide, mixed oxo-flurocomplexes of W(IV), WO2F2, WOF4, mixed oxo-chlorocomplexes of W(IV), WO2Cl2, WOCl4, W(CO)6, H2WO4(aq,), MoO3, Na2MoO4, and H4PMo11VO40;
• and
• (b) obtaining the compound of formula (I).