Synthesis of thiocyanohydrins from epoxides using quaternized amino functionalized cross-linked polyacrylamide as a new solid–liquid phase-transfer catalyst

Anticancer and Anti-inflammatory Sulfur-Containing Semisynthetic Derivatives of Sarcophine

“…13) Although the reaction mechanism was proposed in 1950's, the thiocyanohydrin intermediate was not isolated until recently. [13][14][15] Cyclic epoxides yield trans b-hydroxy thiocyanates under reasonably mild conditions and with proper catalyst. [14][15][16] These reactions are known to proceed with high regioselectivity, almost exclusively yielding anti-Markovnikov's products.…”

“…[13][14][15] Cyclic epoxides yield trans b-hydroxy thiocyanates under reasonably mild conditions and with proper catalyst. [14][15][16] These reactions are known to proceed with high regioselectivity, almost exclusively yielding anti-Markovnikov's products. [14][15][16] However in sarcophine, where the epoxide attached to a 14-membered macrocycle, sulfur attack was exclusively on the more substituted carbon as per Markovnikov's rule, suggesting a carbocation intermediate followed by a thermodynamically stable product.…”

“…[14][15][16] These reactions are known to proceed with high regioselectivity, almost exclusively yielding anti-Markovnikov's products. [14][15][16] However in sarcophine, where the epoxide attached to a 14-membered macrocycle, sulfur attack was exclusively on the more substituted carbon as per Markovnikov's rule, suggesting a carbocation intermediate followed by a thermodynamically stable product. The syn addition of the nucleophile resulted in the cis b-hydroxy thiocyanate 3.…”

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

“…3 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, 4 HSCN, 5 DDQ, 6 Ti(O i Pr) 4 , 7 Ph 3 P(SCN) 2 , 8 TiCl 3 , 9 ZnCl 2 , 9 Pd(PPh 3 ) 4 , 10 TMSNCS/TBAF, 11 poly[N-(2-aminoethyl) acrylamido]trimethyl ammonium chloride (PTC), 12 GaCl3, 13 selectfluor, 14 metalloporphyrins, 15 dichloro(5,10,15,20-tetraphenylporphyrin) phosphorus (V) chloride [P(TPP)Cl 2 ]Cl, 16 tetraarylporphyrins, 17 PEG-SO3H, 18 thioxanthenone-fused azacrown ethers, 19 silica sulfuric acid, 20 Dowex-50X8, 21 2,6-bis[2-(o-aminophenoxy)methyl]-4-bromo-1-methoxybenzene (BABMB), 22 phenol-containing macrocyclic diamides, 23 2-phenyl-2-(2-pyridyl)imidazolidine (PPI), 24 B(HSO 4 ) 3 25 and Al(HSO 4 ) 3 /SiO 2 26 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.…”

B(HSO4)3: a novel and efficient solid acid catalyst for the regioselective conversion of epoxides to thiocyanohydrins under solvent-free conditions

“…3 The formation of thiirane from the reaction of epoxide and thiocyanate ion has been explained to occur through the intermediacy of the corresponding β-hydroxy thiocyanate, but this intermediate has not been isolated due to its rapid conversion to the corresponding thiirane. 4 Thus, few methods are reported for the preparation of β-hydroxy thiocyanates, [5][6][7][8][9][10][11] but some of these methods are limited to specific epoxides and are not applicable as versatile reagents in the preparation of β-hydroxy thiocyanates and suffer from disadvantages such as long reaction times, low regioselectivity, using of organic solvents, using of expensive catalysts or involve high temperature reaction conditions. Therefore, it seems that there is still a need for development of novel methods that proceed under mild and eco-friendly conditions.…”