Concerning the mechanism of formation of oxygen difluoride

Abstract

alyst-substrate adducts and the dihydrides derived from them is the trans disposition of the substrate and diphosphine chelate rings in the former case and the cis disposition in the latter (Figure 9). Unfortunately, all attempts to intercept and examine the dihydride intermediates in these reactions, and thus to probe this theme directly, have thus far been unsuccessful. This failure is consistent with the endothermicity of the H2 oxidative addition step that is a feature of the behavior depicted in Figure 9.Acknowledgment. Support of this research through a grant from the National Science Foundation (CHE 82-17950) and a generous loan of rhodium from Johnson-Matthey Co. are gratefully acknowledged. The NMR facilities used in this research were supported in part through The University of Chicago Cancer Center Grant No. NIH-CA-14599.

Selective fluorination of m-tyrosine by OF2

“…The The effect of the electron donating OH substituent at the ortho-, meta-and para-positions on the fluorination of aromatic amino acids by OF 2 was studied using o-, m-and p-tyrosine as the substrates. Contrary to expectations, MT was the only isomer shown by 19 F NMR spectroscopy and HPLC to be fluorinated by OF 2 , showing that OF 2 is, in this instance, a highly selective fluorinating agent.…”

“…1). After analysis of the reaction mixtures by 19 F NMR spectroscopy, each sample was spiked with known quantities (1.03 and 2.07 AE 0.04 mmol) of the internal standard, m-fluoro-DL-tyrosine. Fluorine-19 NMR peak integrations of the spiked reaction mixtures were then used to calculate reaction yields (Table 1).…”

“…The U-tube, containing an equimolar mixture of anhydrous KF and KFÁ2H 2 O, was pressurized with [ 18 F]F 2 (typically 60 AE 5 mmol of F 2 was used) and was agitated for 110 min at room temperature, after which the gas was passed through the TAG solution. The fluorinated reaction mixture was then analyzed by 19 source at one end, was fed through the sidearm of the Y-piece into the reaction vessel. The other arm of the Ypiece was connected to a separate length of 1/16 in.…”

“…Two 0.100 mL aliquots of 0.010 M m-fluoro-DL-tyrosine were then added stepwise to each reaction mixture, which was analyzed by 19 F NMR spectroscopy after each addition. Each aliquot contained 1.03 AE 0.04 mmol of m-fluoro-DL-tyrosine, so that 19 F NMR peak integrations could be used to calculate the FMT isomer yields.…”

“…Several synthetic routes have been used to prepare OF 2 , including the reaction of fluorine with aqueous alkali solutions [15], 60% HClO 4 [16], H 5 IO 6 [17], hydrated alkali fluorides [18], or HOF [19]. More recently, Satyamurthy et al [20] reported the www.elsevier.com/locate/fluor Journal of Fluorine Chemistry 129 (2008) [22][23][24][25][26][27] (1) formation of [ 18 F]OF 2 as a reaction byproduct (up to 5% for double shoot and up to 20% for the single shoot irradiation methods) under the high-pressure and high-energy irradiation conditions of a proton cyclotron gas target using the nuclear reaction, 18 O(p, n) 18 F and according to Eqs.…”