We report a method for labeling arylvinyltrifluoromethanes with carbon-11 (t 1/2 = 20.4 min) as representatives of a new radiolabeled chemotype that has potential for developing radiotracers for biomedical imaging with positron emission tomography. Treatment of (E)-arylvinyl(phenyl)iodonium tosylates (1a−1k) with [ 11 C[CuCF 3 gave the corresponding [ 11 C]arylvinyltrifluoromethanes ([ 11 C]2a−[ 11 C]2k) in high radiochemical yields (90−97%) under rapid (2 min) and mild (60 °C) conditions.
Efficient methods for labeling aryl trifluoromethyl groups to provide novel radiotracers for use in biomedical research with positron emission tomography (PET) are keenly sought. We report a broad‐scope method for labeling trifluoromethylarenes with either carbon‐11 (t1/2=20.4 min) or fluorine‐18 (t1/2=109.8 min) from readily accessible aryl(mesityl)iodonium salts. In this method, the aryl(mesityl)iodonium salt is treated rapidly with no‐carrier‐added [11C]CuCF3 or [18F]CuCF3. The mesityl group acts as a spectator allowing radiolabeled trifluoromethylarenes to be obtained with very high chemoselectivity. Radiochemical yields from aryl(mesityl)iodonium salts bearing either electron‐donating or electron‐withdrawing groups at meta‐ or para‐ position are good to excellent (67–96 %). Ortho‐substituted and otherwise sterically hindered trifluoromethylarenes still give good yields (15–34 %). Substituted heteroaryl(mesityl)iodonium salts are also viable substrates. The broad scope of this method was further exemplified by labeling a previously inaccessible target, [11C]p‐trifluoromethylphenyl boronic acid, as a potentially useful labeling synthon. In addition, fluoxetine, leflunomide, and 3‐trifluoromethyl‐4‐aminopyridine, as examples of small drug‐like molecules and candidate PET radioligands, were successfully labeled in high yields (69–81 %).
The unique reactivity of γ-silyl allenyl esters is described. taking advantage of the silyl group as a fluoride acceptor, these allenoates readily underwent addition to a variety of electrophiles to selectively produce products with all-carbon quaternary centers or allenoate dicarbinols. these dicarbinols were subsequently converted to novel highly substituted 6-hydro-2-pyrones.
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