The enantioselective hydrogenation of N-(1-phenylethylidene)aniline using cationic iridium complexes with chiral phosphinooxazoline ligands was studied as a chemical probe to assess the potential of ionic liquid/carbon dioxide (IL/CO2) media for, multiphase catalysis. The biphasic system leads to activation, tuning, and immobilization of the catalyst that would be impossible in classical organic solvent systems or in either of the two unconventional media separately. In particular it is demonstrated that (i) the presence of CO2 can be beneficial or even mandatory for efficient hydrogenation in the IL; (ii) the precursor is activated in the IL by anion exchange allowing one to use in situ catalysts; (iii) the anion of the IL greatly influences the selectivity of the catalyst; (iv) the products are readily isolated from the catalyst solution by CO2 extraction without cross contamination of IL or catalyst; and (v) the IL leads to enhanced stability of the catalyst. These results are corroborated and rationalized on the basis of the physicochemical properties of the biphasic medium and the chemical characteristics of the catalytic systems.
Planar 131 I scintigraphy is routinely used to detect radioiodineavid metastases of differentiated thyroid carcinoma (DTC). However, the modality has limitations, such as low sensitivity and lack of anatomic landmarks. We investigated whether SPECT with integrated low-dose CT may have additional value over planar imaging in detecting residue and metastases in DTC patients. Methods: We studied 117 consecutive thyroidectomized DTC patients. On 2 different hybrid dual-head g-cameras (55 patients on one camera and 62 on the other), 108 patients underwent 131 I diagnostic imaging and SPECT/ CT, and 9 underwent posttherapeutic 131 I planar imaging and SPECT/CT. We assigned an incremental value to SPECT/CT when it provided better identification and interpretation of the foci of radioiodine uptake, more correct anatomic localization and characterization, and precise differentiation between tumor lesions and physiologic uptake. Results: Planar imaging showed 116 foci of uptake in 52 of 117 patients, and SPECT/CT showed 158 foci in 59 of 117 patients, confirming all foci seen on planar imaging but identifying an additional 28 occult foci in 10 of 52 patients. Fourteen occult foci were shown on SPECT/CT in 7 further patients whose planar imaging findings were negative. SPECT/ CT correctly characterized 48 foci unclear on planar imaging, also defining location and extent. SPECT/CT was a determinant in classifying as neoplastic those foci for which planar imaging seemed to exclude malignancy, discriminating between residue and lymph node metastases in the neck, some of which were adjacent to salivary glands and had been missed on planar imaging. SPECT/CT also showed occult lesions in the mediastinum, abdomen, and pelvis and identified small bone metastases unsuspected on planar imaging. Globally, SPECT/CT had an incremental value over planar imaging in 67.8% of patients, modified therapeutic management in 35.6% of positive cases, and avoided unnecessary treatment in 20.3% of patients with only single benign lesions or physiologic uptake. Conclusion: 131 I SPECT/CT improved planar data interpretation, showing a higher number of DTC lesions, more precisely localizing and characterizing DTC foci, and more correctly differentiating between physiologic uptake and metastases, thus permitting the most appropriate therapeutic approach to be chosen. A wider use of this method is suggested complementary to planar imaging in selected DTC patients. Convent ional planar 131 I whole-body scintigraphy, in association with serum thyroglobulin measurement, is still considered the routine diagnostic procedure in patients with well-differentiated thyroid carcinoma (DTC). This modality is used in the detection of both thyroid tissue residue and local and distant metastases, after thyroidectomy for staging and after radioiodine ablation for restaging and long-term follow-up (1). A sensitivity of 45%275% and a specificity of 90%2100% have been reported in the literature for diagnostic planar 131 I whole-body imaging in detecting recurrences or me...
A new immobilization scheme for enantioselective catalysts was developed by using a combination of ionic liquids and compressed CO2. Under continuous flow conditions, stable conversion and asymmetric induction was achieved over more than 60 h in the enantioselective Ni‐catalyzed hydrovinylation of styrene. While the ionic liquid dissolves and activates the organometallic catalyst in a tuneable manner, the presence of compressed CO2 greatly facilitates mass transfer and gives easy access to continuous processes (see the schematic representation).
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