We report a general method for the labeling of both CF 3 and CF 2 H groups in a broad range of chemical settings (aryl, oxide, sulfide). The method utilizes frustrated Lewis pair mediated selective CÀ F activation to formally substitute fluorine-19 with fluorine-18 in a two-step defluorination/radiofluorination process, and as such can utilize the target compounds as starting materials. The radiotracer precursors can be isolated as stable salts prior to radiofluorination. The method delivers good radiochemical yields and molar activities (up to 35.2 � 6.5 % non-decay corrected isolated activity yields and 12.0 � 1.7 GBq μmol À 1 molar activities) and is shown to be applicable to biologically relevant compounds. The ability to utilize the target compound as the starting material and the synthetic simplicity of the method coupled with the ever-increasing use of CF 3 and CF 2 H groups in pharmaceuticals makes this method attractive for drug and radiotracer development.In molecular imaging, fluorine-18 (t 1/2 � 110 min) finds use as the most suitable radionuclide for positron-emission tomography (PET). [1] PET utilizes radiotracers that contain (most commonly) the positron-emitting fluorine-18 to noninvasively image biological tissue and organs in real-time. Most notably, PET is utilized in diagnostic medicine but has also found application in pharmacokinetic studies. [2] Recent attention has turned to the incorporation of fluorine-18 into difluoromethyl and trifluoromethyl groups due to their increasing presence in bioactive molecules as bioisosteres. [3] The ability to readily label CF 3 and CF 2 H groups with fluorine-18 in biologically relevant molecules for use in PET would directly benefit drug development, pharmacokinetic studies and biological imaging. [4] A number of reports have demonstrated incorporation of fluorine-18 into CF 2 H and CF 3 (Figure 1, A). [5] For example, halogen exchange (Halex) has been utilized to generate fluorine-18 labeled CF 2 H and CF 3 groups, most successfully with bromide leaving groups. [5a-k] The harsh reaction conditions required for exchange of CÀ X bonds

The effects of aging on the repair bond strengths of resin-modified glass-ionomer cements after different methods of surface conditioning were studied. Surface conditioning methods included the following: maleic acid; maleic acid with resin application; polyacrylic acid; polyacrylic acid with resin application. Shear bond testing between the aged and new material was carried out with an Instron Universal testing machine. Surface conditioning with maleic acid and resin application gave the highest repair bond strengths at 3 and 6 months. There was, however, no statistically significant difference in bond strengths between the different treatment groups after both 3 and 6 months storage. Intergroup comparisons revealed no significant difference in failure modes after both storage periods. For all treatment groups, no significant difference in repair bond strengths was noted between storage after 1 week, 3 and 6 months. There appears to be a general decrease in repair bond strengths for all treatment groups after 3 months storage. The clinical repair of resin-modified glass-ionomer cements after this period of time is therefore not recommended.

Frustrated Lewis pairs (FLP) comprising of B(C6F5)3 (BCF) and 2,4,6-triphenylpyridine (TPPy), P(o-Tol)3 or tetrahydrothiophene (THT) have been shown to mediate selective C–F activation in both geminal and chemically equivalent distal...

We report a general method for the labeling of both CF 3 and CF 2 H groups in a broad range of chemical settings (aryl, oxide, sulfide). The method utilizes frustrated Lewis pair mediated selective CÀ F activation to formally substitute fluorine-19 with fluorine-18 in a two-step defluorination/radiofluorination process, and as such can utilize the target compounds as starting materials. The radiotracer precursors can be isolated as stable salts prior to radiofluorination. The method delivers good radiochemical yields and molar activities (up to 35.2 � 6.5 % non-decay corrected isolated activity yields and 12.0 � 1.7 GBq μmol À 1 molar activities) and is shown to be applicable to biologically relevant compounds. The ability to utilize the target compound as the starting material and the synthetic simplicity of the method coupled with the ever-increasing use of CF 3 and CF 2 H groups in pharmaceuticals makes this method attractive for drug and radiotracer development.In molecular imaging, fluorine-18 (t 1/2 � 110 min) finds use as the most suitable radionuclide for positron-emission tomography (PET). [1] PET utilizes radiotracers that contain (most commonly) the positron-emitting fluorine-18 to noninvasively image biological tissue and organs in real-time. Most notably, PET is utilized in diagnostic medicine but has also found application in pharmacokinetic studies. [2] Recent attention has turned to the incorporation of fluorine-18 into difluoromethyl and trifluoromethyl groups due to their increasing presence in bioactive molecules as bioisosteres. [3] The ability to readily label CF 3 and CF 2 H groups with fluorine-18 in biologically relevant molecules for use in PET would directly benefit drug development, pharmacokinetic studies and biological imaging. [4] A number of reports have demonstrated incorporation of fluorine-18 into CF 2 H and CF 3 (Figure 1, A). [5] For example, halogen exchange (Halex) has been utilized to generate fluorine-18 labeled CF 2 H and CF 3 groups, most successfully with bromide leaving groups. [5a-k] The harsh reaction conditions required for exchange of CÀ X bonds