1-Phenylethyl trifluoroacetate

The high reaction orders in acid observed in these polymerizations further support their role as both activator and initiator [101,102], In addition, because acid adds only slowly to styrene to form 1-phenylethyl triflu-oroacetate, the polymerization rate increases in the presence of preformed 1-phenylethyl trifluoroacetate initiator, which is then activated by excess... 

Trifluoromethyl-l-phenylethyl tosylate has been used to differentiate as shown in Table 1, the solvolytic power of three fluorinated solvents and to compare these with formic and acetic acids The three fluorinated solvents are trifluoroacetic acid, trifluoroethanol, and 1,1,1,3,3,3-hexafluoroisopropyl alcohol [55]... 

Treatment of 7V-(2-hydroxy-2-phenylethyl)-2-aminomethylthiophene with polyphosphoric acid results in formation of 4-phenyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine (1) in 89% yield. If trifluoroacetic acid is used, however, the product, obtained in 100% yield, is a 4 1 mixture of 7-phenyl-4,5,6,7-tetrahydrothieno[3,2-c]pyridine 2 and 1. 

Asymmetric reduction of (5s)-sulfmimine 110 with diisobutylaluminum hydride (DIBAL) afforded a diastereomeric mixture of sulfinamides 111 in 92% yield and in a ratio of 96 4.34 Use of sodium boron hydride, lithium aluminum hydride, or lithium alkoxyaluminum hydride resulted in lower optical yields.33,34,75 The sul-finyl group can be removed by treating 111 with trifluoroacetic acid (TFA) and methanol to give a-phenylethyl amine (112). 

Merucathinone was synthesized by Wolf and Pfander (79) from rerr-butoxycar-bonyl-L-alanine (Scheme 4). Treatment with n-butyllithium and styryllithium as before formed 20, which was deblocked with trifluoroacetic acid to give merucathinone (6), isolated as the oxalate. As assessed by treatment with (+)-l-phenylethyl isocyanate and HPLC, the optical purity of 6 was greater than 97%. Treatment of r-BOC-L-alanine with 3 equiv of phenyllithium gave ketone 21, which was deblocked as before to provide a short synthesis of cathinone (2), isolated as its hydrochloride (enantiomeric excess >95%) (19). 

The enantiomerically pure 1,3,5-hexahydrotriazine 1, synthesized by coupling (S)-l-phenylethyl-amine with paraformaldehyde, underwent addition to acyl chloride affording TV-chloromethyl amides 2 that were converted to the corresponding amidals 3. In order to synthesize optically active TV-substituted 4-imidazolidinones 5 (protected oc-amino acids), the amidal 3 was cyclized in dry dichloromethane with mercury(II) trifluoroacetate as the electrophile to give 4168. 

The mechanism for the initiation step of the polymerization was investigated using the stoichiometric reaction of 73-allylnickel trifluoroacetate (14) with 1-phenylethyl isocyanide labeled with 13C at the isocyano carbon atom (Scheme 18) [24, 25]. 13C NMR measurements revealed that addition of three... 

Both primary and secondary carbocations with )8-phenyl substituents usually give evidence of aryl participation. For example, isotopically labeled carbons are scrambled to some extent during solvolysis of j8-phenylethyl tosylates, A bridged-ion intermediate or rapidly reversible rearrangement of a primary carbocation could account for the randomization of the label. The extent of label scrambling increases as solvent nucleophilicity decreases. The data are shown in Table 5.19. This trend can be attributed to competition between Sn2 displacement by solvent and ionization with participation of the aryl group. While substitution in more nucleophilic solvents such as ethanol proceeds almost exclusively by direct displacement, the non-nucleophilic solvent trifluoroacetic acid leads to complete randomization of the label. 

Phenylethanol Trifluoroacetic anhydride 2-Phenylethyl trifluroacetate (83%) Trifluoroacetic acid... 

Table 5.8 lists relative rates of solvolysis of 1-phenylethyl esters and halides in 80% aqueous ethanol at 75°C. Most of the values in this table have been estimated, and the relative reactivities have more qualitative than quantitative significance. The relative reactivities parallel electron withdrawal by substituents in an anticipated fashion. Trifluoroacetate is about 10 times more reactive than acetate, and p-nitrobenzenesulfonate is about 10 times more reactive than p-toluenesulfonate. The order of reactivity of the halide leaving groups, I > Br > Cl F, is interesting in... 

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