2.2.2- trifluoroethanol acidity benzene

The synthesis of array L7 is reported in Fig. 8.22. Compound 8.38 was reacted simultaneously with amines (Mi, two representatives), aldehydes (Mi, five representatives), and isonitriles (Ms, two representatives) to give 10 compounds (not all the combinations were reacted). The reaction was performed in trifluoroethanol (TFE), another hybrid fluorous-organic solvent (step a. Fig. 8.22), and after evaporation of the TFE, the crude product 8.39 was purified by two-phase extraction between fluorous solvents and benzene (step b). After evaporation of the solvent, the fluorous tag was cleaved with TBAF (step c) and a triphasic extraction (step d, Eig. 8.22) was performed to remove the fluorosilane tag and acid 8.38-related impurities extracted into the fluorous layer. Excess TBAE and TBAE-related impurities partitioned into the acidic aqueous layer. Yields and purities of the synthetic protocol are reported together with the structures of the library members L7a-j in Table 8.2. 

Solution calorimetry of the molecular probes pyrrole, A-methylpyrrole, benzene, and toluene in 35 solvents has been used by Catalan el al. to determine a solvent HBA basicity scale, ranging from the gas phase to HMPT [31a]. Analogously, a solvent HBD acidity scale was derived calorimetrically using A-methylimidazole and A-methylpyrrole as probe molecules in 3 6 solvents, ranging from the gas phase to 2,2,2-trifluoroethanol [31b]. 

In benzene and with acidic alcohols such as 2,2,2-trifluoroethanol or phenol as cosolvents, the rate of hydrogenation of alkyne by Wilkinson s catalyst, [RhCKPPhsIs], is accelerated, while that of C==C bonds does not change, which allows selective hydrogenation of alkynes. [Rh(COD)(PPh3)(Py)]PF6 can also catalyze the selective reduction of 1-alkynes to 1-alkenes in the presence of benzoate ion. For example, phenylacetylene is slowly reduced with 1 equiv. of D2 (1 atm) to ds-PhCD=CHD by [Rh(COD)(PPh3)(Py)]PF6 in the presence of an excess of Et3NH PhC02. Thus compound (74) is converted selectively to (75). ... 

Diastereoselective U-4CR of chiral y-keto acid 10s with 6i and lx in 2,2,2-trifluoroethanol at room temperature provides y-lactam 205 in a 78% yield as a single diastereomer. The diastereoselectivity is believed to arise from the exclusive axial approach of small nucleophiles onto the carbonyl group of l,3-dioxan-4-ones [82]. Deprotection of the acetonide with catalytic amount of CSA in MeOH followed by protection of the diol to the corresponding diacetate and further treatment with catalytic amount of CSA in benzene provides the A-acylindole 206. The A-acylindole... 

The photochemical preparation of benzvalene was prompted by this proposal. Further strong support for benzvalenes as intermediates in the photochemistry of benzene and substituted benzenes also came from experiments in alcohol solvents under mild acidic conditions. " The primary products are bicy-clo[3.1.0]hexene derivatives resulting from alcohol addition. Moreover, on photolysis of benzene-1,3,5-d, and benzene-dg in 2,2,2-trifluoroethanol (TFE), the products formed resulted from selective protonation at Cg with endo stereochemistry (Eq. (46.5)). ... 

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