Trifluoromethyl phenyl isothiocyanate

Ricci and co-workers introduced a new class of amino- alcohol- based thiourea derivatives, which were easily accessible in a one-step coupling reaction in nearly quanitative yield from the commercially available chiral amino alcohols and 3,5-bis(trifluoromethyl)phenyl isothiocyanate or isocyanate, respectively (Figure 6.45) [307]. The screening of (thio)urea derivatives 137-140 in the enantioselective Friedel-Crafts reaction of indole with trans-P-nitrostyrene at 20 °C in toluene demonstrated (lR,2S)-cis-l-amino-2-indanol-derived thiourea 139 to be the most active catalyst regarding conversion (95% conv./60h) as well as stereoinduction (35% ee), while the canditates 137, 138, and the urea derivative 140 displayed a lower accelerating effect and poorer asymmetric induction (Figure 6.45). The uncatalyzed reference reaction performed under otherwise identical conditions showed 17% conversion in 65 h reaction time. 

Transesterification. Zwitterionic adduct of 4-pyrrolidinopyridine and an electron-deficient aryl isothiocyanate (e.g., p-nitrophenyl and 3,5-bis(trifluoromethyl)phenyl isothiocyanates) catalyzes transesterification of methyl esters, requiring only stoichiometric quantity of the alcohol. The reaction is best performed by azeotropic refluxing, with assistance of 5A-molecular sieves to absorb the liberated MeOH. 

The superbase DBU was chosen as catalyst for the ROP of lactide because of its fast kinetics, high efficiency, and prevention of transesterification. However, it was decided to add bis(3,5-trifiuoromethyl)phenyl cyclohexylthiourea (thiourea) as co-catalyst to further increase the efficiency and overcome possible steric hindrance arising from the bulkiness of macromolecular initiators. The thiourea was synthesized according to Pratt et al. [41]. Briefly, 3,5-bis(trifluoromethyl)phenyl isothiocyanate (3.37 ml, 18.5 mmol) and anhydrous tetrahydrofuran (20 ml) were added to a flame-dried two-neck round bottom flask. Cyclohexylamine (2.11 ml, 18.5 mmol) was added dropwise via a syringe at room temperature to the stirring solution. After... 

Phenyl isothiocyanate 4-Nitrophenyl isothiocyanate Trifluoromethyl phenyl isothiocyanate 4-Cyanophenyl isothiocyanate 4-Methoxyphenyl isothiocyanate 4-Fluorophenyl isothiocyanate 4-Methylphenyl isothiocyanate 2-Fluoro-5-(trifluoromethyl)phenyl isothiocyanate 4-Methyl-3-(trifluoromethyl)phenyl isothiocyanate 4-Fluoro-3-(trifluoromethyl)phenyl isothiocyanate 3,5-Bis(trifluoromethyl)phenyl isothiocyanate 1,4-Phenylene diisothiocyanate... 

Methyl-3-(trifluoromethyl)phenyl isothiocyanate Figure 2.25 Isothiocyanates. 

A(-(Benzimidoyl)imines (191 R = 2,4,6-Me3QH2) undergo cycloaddition with CS2 to yield 3,6-dihydro-6,6-bis(trifluoromethyl)-2/f-l,3,5-thiadiazine-2-thiones (192). Addition to phenyl isothiocyanate, however, is nonregioselective and produces a mixture of the 6-phenylimino-2/f-1,3,5-thiadiazine (193 51%) and the isomeric 3,6-dihydro-2/f-l,3,5-triazine-2(l//)-thione (194 28%) (Scheme 29) <84ZN(B)1442>. 

Copper iodide catalyzes the reaction of 2-amino-3-hydroxypyridines with phenyl isothiocyanates to form 2-aminooxazolo[4,5-l ]pyridines in good yields (Scheme 43). The yield is susceptible to the nucleophihcity of the 2-amino-3-hydroxypyridines and the electrophilicity of the isothiocyanate. For example, a trifluoromethyl group on the phenyl isothiocyanate provided strong yields (84-92%) (14TL1296). 

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