ChemInform Abstract: Fast, Efficient and Regioselective Conversion of Epoxides to β‐Hydroxy Thiocyanates with NH4SCN/Zeolite Molecular Sieve 4 Å under Solvent‐Free Conditions.

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Epoxides (oxiranes) are one of the most useful synthetic intermediates in organic synthesis and a vast variety of protocols have been developed for regioselective ring opening of these compounds. Nucleophilic ring opening of epoxides with thiocyanate ion usually gives thiiranes and numerous articles exhibit the importance of this synthetic method. It is explained that the formation of thiiranes from the reaction of epoxides with thiocyanate ion has been occurred through the intermediacy of the corresponding β-hydroxy thiocyanates; however, this intermediate has not been isolated due to its rapid conversion to the corresponding thiirane. Literature review shows that hydroquinone, HSCN, DDQ, Ti(OPr)4, Ph3P(SCN)2, TiCl3, ZnCl2, Pd(PPh3)4, TMSNCS/TBAF, poly[N-(2-aminoethyl) acrylamido]trimethyl ammonium chloride (PTC), GaCl3, selectfluor, metalloporphyrins, dichloro(5,10,15,20-tetraphenylporphyrin) phosphorus (V) chloride [P(TPP)Cl2]Cl, tetraarylporphyrins, PEG-SO3H, thioxanthenone-fused azacrown ethers, silica sulfuric acid, Dowex-50X8, 2,6bis[2-(o-aminophenoxy)methyl]-4-bromo-1-methoxybenzene (BABMB), phenol-containing macrocyclic diamides, 2phenyl-2-(2-pyridyl)imidazolidine (PPI), B(HSO4)3 and Al(HSO4)3/SiO2 are the reagents which stabilize the produced β-hydroxy thiocyanate and therefore inhibit from the conversion to thiirane. In contrast to above mentioned protocols, it was also reported that conversion of epoxides to β-hydroxy thiocyanates can be achieved with high quantities of NH4SCN in the absence of any catalyst. Though the reported methods are useful for preparation of β-hydroxy thiocyanates from epoxides, however, some of these protocols suffer from disadvantages such as long reaction times, use of volatile organic solvents and expensive reagents, low regioselectivity and high temperature reaction conditions. Thus, the development and introduction of convenient methods which use green and mild reaction conditions are practically concerned and still in demand. Herein, we wish to introduce zeolite molecular sieve 4 A as a reusable promoter for fast, efficient and perfect regioselective conversion of various epoxides to their corresponding β-hydroxy thiocyanates under solvent-free conditions at room temperature (Scheme 1).