Bridging Titanium Nitrido Complexes Containing A Linear Ti-N-Ti Core with A Two-Coordinate Nitrido Ligand.

A series of titanium m2-nitrido complexes supported by the triamidoamine ligand Xy-N3N (Xy-N3N = {(3,5-Me2C6H3)NCH2CH2}3N3-) is reported. The titanium azido complex [(Xy-N3N)TiN3] (1-N3), prepared by salt metathesis of the chloride complex [(Xy-N3N)TiCl] (1-Cl) with NaN3, reacted with lithium metal or with alkali metal naphthalenides (alkali metal M = Na, K, and Rb) in THF to give the corresponding dinuclear m2-nitrido complexes M[(Xy-N3N)Ti=N-Ti(Xy-N3N)] (2-M; M = Li, Na, K, Rb). Single crystal X-ray diffraction studies of 2-Li, 2-Na, and 2-K revealed alkali metal dependent structures in the solid state. While 2-Li and 2-K contain a m2-nitrido ligand with a linear Ti-N-Ti core, 2-Na includes a m3-nitrido ligand as part of a T-shape Ti2NaN fragment with the sodium cation weekly coordinated to the nitrido nitrogen atom. When the synthesis of the nitrido complexes was carried out in the presence of excess alkali metals, selective decomposition of the nitrido complexes was observed affording some intractable titanium species along with the trialkali metal salts [M3(Xy-N3N)] (3-M) (M = Li, Na, K, and Rb). These salts were also prepared by deprotonation of (Xy-N3N)H3 with the corresponding alkali metal hexamethyldisilazide and characterized by multinuclear NMR spectroscopy as well as single crystal X-ray diffraction.

Benzylic C(sp3 )-H Bond Oxidation with Ketone Selectivity by a Cobalt(IV)-Oxo Embedded in a ß-Barrel Protein.

Artificial metalloenzymes have emerged as biohybrid catalysts that allow to combine the reactivity of a metal catalyst with the flexibility of protein scaffolds. This work reports the artificial metalloenzymes based on the ß-barrel protein nitrobindin NB4, in which a cofactor [CoII X(Me3 TACD-Mal)]+ X- (X=Cl, Br; Me3 TACD=N,N' ,N''-trimethyl-1,4,7,10-tetraazacyclododecane, Mal=CH2 CH2 CH2 NC4 H2 O2 ) was covalently anchored via a Michael addition reaction. These biohybrid catalysts showed higher efficiency than the free cobalt complexes for the oxidation of benzylic C(sp3 )-H bonds in aqueous media. Using commercially available oxone (2KHSO5 ⋅ KHSO4 ⋅ K2 SO4 ) as oxidant, a total turnover number of up to 220 and 97 % ketone selectivity were achieved for tetralin. As catalytically active intermediate, a mononuclear terminal cobalt(IV)-oxo species [Co(IV)=O]2+ was generated by reacting the cobalt(II) cofactor with oxone in aqueous solution and characterized by ESI-TOF MS.

Formate complexes of tri- and tetravalent titanium supported by a tris(phenolato)amine ligand.

Titanium(III) and titanium(IV) formate complexes supported by the sterically encumbering tris(phenolato)amine ligand (H3(O3N) = tris(4,6-di-tert-butyl-2-hydroxybenzyl)amine) are described. Salt metathesis of the chlorido precursor [(O3N)TiCl] (1-Cl) with sodium formate in a 2 : 1 ratio in THF gave a dimer of sodium dititanium triformate units with 12-membered ring [Na{(O3N)Ti}2(µ-OCHO-ηO:ηO')3]2 (3-Na) when crystallized from acetonitrile. Complex 3-Na was also prepared by reacting the previously reported terminal formate complex [(O3N)Ti(OCHO)] (2) with excess sodium formate. Salt metathesis of 1-Cl with potassium formate gave a tetratitanium cluster of the composition [K3{(O3N)Ti}4(OCHO)7] (3-K) which can be also obtained by treating 2 with potassium formate. In 3-K both Ti and K centers are six-coordinate. The titanium(III) complexes [(O3N)Ti(L)] (4-L, L = THF, THP, Et2O) and solvent free dimeric [(O3N)Ti]2 (5) were synthesized by reduction of 1-Cl with sodium sand or magnesium in THF, THP, Et2O, and n-pentane, respectively. The tert-butyl formate adduct of titanium(III)-[(O3N)Ti(tBuOCHO)] (6) was isolated by reacting 4-L or 5 with tert-butyl formate. Complex 6 is thermolabile and slowly decomposed in solution to produce a formate-bridged mixed-valence titanium(III)/titanium(IV) complex [{(O3N)Ti}2(µ-OCHO-ηO:ηO')] (7) which further decomposed to a mixture containing 2, [(O3N)Ti(OH)] and [(O3N)Ti-O-Ti(O3N)]. All new complexes were isolated in moderate to good yields and fully characterized by elemental analysis, 1H and 13C NMR spectroscopy, and single crystal X-ray diffraction analysis. For the titanium(III) complexes solution magnetic moments were measured by the Evans method and EPR spectra recorded as toluene glass at 77 K.

Solvent-Dependent Oxidative Addition and Reductive Elimination of H2 Across a Gallium-Zinc Bond.

H2 adds reversibly across the metal-metal bond of [(BDI)Ga(H)-Zn(tmeda)(thf)][BAr4 F ] (BDI=[HC{C(CH3 )N(2,6-iPr2 -C6 H3 )}2 ]- , TMEDA=N,N,N',N'-tetramethylethylenediamine, BAr4 F- =[B(C6 H3 -3,5-(CF3 )2 )4 ]- ). Due to the stabilising effect of solvent coordination, hydrogenation products [(BDI)GaH2 ] and [(tmeda)ZnH(thf)][BAr4 F ] are favoured in THF solution, but THF-free mixtures of [(BDI)GaH2 ] and [(tmeda)ZnH(OEt2 )][BAr4 F ] are predisposed towards entropically driven dehydrogenation to [(BDI)Ga(H)-Zn(tmeda)][BAr4 F ] in fluorobenzene solution.

Silver-Catalyzed Carbon Dioxide Fixation on Alkynylindenes.

The synthesis of polycyclic indene derivatives via silver-catalyzed carbon dioxide fixation on 2-alkynylindene derivatives was achieved by nucleophilic addition of the indenyl anion to carbon dioxide involving carbon-carbon bond formation and subsequent intramolecular cyclization to the alkyne part activated by a silver catalyst. This cascade process could be applied to various substrates to obtain the corresponding products in high yields. The endo/exo selectivity of the cyclization could be controlled by the steric or electronic effect of the substituents on the substrates, and 6-endo-selective cyclization was realized to afford α-pyrone-fused indenes.

Kolbe-Schmitt type reaction under ambient conditions mediated by an organic base.

The combined use of an organic base for resorcinols realized a Kolbe-Schmitt type reaction under ambient conditions. When resorcinols (3-hydroxyphenol derivatives) were treated with DBU under a carbon dioxide atmosphere, nucleophilic addition to carbon dioxide proceeded to afford the corresponding salicylic acid derivatives in high yields.

Evaluation of Fibrous Cap Rupture of Atherosclerotic Carotid Plaque with Thin-Slice Source Images of Time-of-Flight MR Angiography.

OBJECTIVE: To investigate the ability of source image of time-of-flight magnetic resonance angiography (TOF-MRA) in the detection of fibrous cap rupture of atherosclerotic carotid plaques. MATERIALS AND METHODS: From the database of radiological information in our hospital, 35 patients who underwent carotid MR imaging and subsequent carotid endoarterectomy within 2 weeks were included in this retrospective study. MR imaging included thin-slice time-of-flight MR angiography, black-blood T1- and T2-weighted imaging. Sensitivity, specificity and accuracy were calculated for the detection of fibrous cap rupture with source image of TOF-MRA. The Cohen k coefficient was also calculated to quantify the degree of concordance of source image of TOF-MRA with histopathological data. RESULTS: Sensitivity, specificity and accuracy in the detection of fibrous cap rupture were 90% (95%CI: 81-98), 69% (95%CI: 56-82) and 79% (95%CI: 71-87) with a k value of 0.59. The false positives (n = 15) were caused by partial-volume averaging between fibrous cap and lumen at the shoulder of carotid plaque. The false negatives (n = 5) were underestimated as partial thinning of fibrous cap. CONCLUSION: Source image of TOF-MRA can be useful in the detection of fibrous cap rupture with high sensitivity, but further technical improvement should be necessary to overcome shortcomings causing image degradation.

Targeted biopsy based on ADC map in the detection and localization of prostate cancer: a feasibility study.

PURPOSE: To investigate the feasibility of targeted biopsy based on an apparent diffusion coefficient (ADC) map in the detection and localization of prostate cancer. MATERIALS AND METHODS: This study included 288 consecutive patients with high or increasing serum prostate-specific antigen (PSA) levels who underwent prostatic magnetic resonance imaging (MRI) examination with an ADC map. Four core-targeted biopsies of low ADC lesions were performed under transrectal-ultrasound guidance with reference to ADC map. The positive predictive values (PPVs) of low ADC lesions were calculated and compared for the peripheral zone (PZ), transition zone (TZ), and anterior portion, respectively. Comparisons of ADC values and sizes between malignant and nonmalignant lesions were also performed. RESULTS: A total of 313 low ADC lesions were detected in 195 patients and sampled by targeted biopsies. The PPVs were 55.3% (95% confidence interval [CI]: 50-61) in total, 61.0% (95% CI: 53-69) for PZ, 50.6% (95% CI: 43-58) for TZ, and 90.9% (95% CI: 81-100) for the anterior portion. The most common nonmalignant pathology of low ADC lesions was hyperplasia, followed by chronic prostatitis. There were significant differences in ADC values and sizes between malignant and nonmalignant low ADC lesions. CONCLUSION: Targeted biopsies could be capable of detecting cancers well wherever they may be in the prostate, although the PPVs varied depending on the location of low ADC lesions.

Detection and localization of prostate cancer with the targeted biopsy strategy based on ADC map: a prospective large-scale cohort study.

PURPOSE: To investigate the usefulness of targeted biopsy strategy based on apparent diffusion coefficient (ADC) maps in the detection and localization of prostate cancer. MATERIALS AND METHODS: Institutional review board approval and informed consent from all participants were obtained. This study included 1448 consecutive patients suspected of having prostate cancer based on PSA level, who were divided into two groups: Group A included 890 patients with low-ADC lesions who underwent targeted and systematic biopsies; Group B included 558 patients with no low-ADC lesions who underwent only systematic biopsies. The cancer detection rates (CDR) of each group, positive predictive value (PPV), and negative predictive value (NPV) of ADC maps were calculated. RESULTS: The CDR was 70.1% for Group A, higher than those for overall patients (48.1%) and for Group B (13.1%) with significant difference (P < 0.001). In the serum, PSA range from 4 to 20 ng/mL, the CDR was higher for the Group A than for the Group B and overall patients with significant differences. PPV and NPV of MR findings were 70.1% and 86.9%, respectively. Especially, the PPV of the MR findings for the anterior portion was as high as 90.1%. Among the false negatives of MR findings, Gleason score proved 6 or smaller in 79.5%, and positive core number was merely one or two in 80.8%. CONCLUSION: The targeted biopsy strategy based on ADC maps can be useful in the detection and localization of prostate cancer with high PPV.

Diffusion-weighted magnetic resonance imaging in the detection of testicular torsion: feasibility study.

PURPOSE: To investigate the feasibility and usefulness of diffusion-weighted magnetic resonance imaging in the detection of testicular torsion. MATERIALS AND METHODS: Institutional Review Board approval and informed consent from all participants were obtained. Consecutive 28 patients with acute scrotal symptoms were included in this study. Fat-suppressed T2-weighted, dynamic subtraction contrast-enhanced, and diffusion-weighted images were obtained in the coronal plane with a 1.5 T MR unit. An apparent diffusion coefficient (ADC) map was reconstructed from the diffusion-weighted images obtained with b-factor of 0 and 800 s/mm(2). Comparisons of ADC values between the affected and nonaffected testes were performed with Mann-Whitney's U-test. RESULTS: Diffusion-weighted and ADC images with diagnostic quality were obtained in 23 out of the 28 patients (82%). In testicular torsion (n = 9), the mean ADC value of the twisted testes was significantly lower than that of the nonaffected testes (0.750 ± 0.297 vs. 1.017 ± 0.165 × 10(-3) mm(2)/sec, P < 0.05). In other scrotal disorders (n = 14), there was no significant difference in the mean ADC value of the testes between the affected and nonaffected side (P = 0.655). The affected-to-nonaffected ratio of ADC value was significantly lower in testicular torsion than that in other scrotal disorders (P < 0.05). CONCLUSION: Diffusion-weighted imaging of the scrotum with testicular ADC measurement can allow for the detection of testicular torsion without any use of contrast media.

Determination of the cutoff level of apparent diffusion coefficient values for detection of prostate cancer.

PURPOSE: The aim of this study was to determine the cutoff level of apparent diffusion coefficient (ADC) values for diagnosing prostate cancer. MATERIALS AND METHODS: A total of 45 consecutive patients with prostate cancer who underwent diffusion-weighted magnetic resonance imaging (MRI) with ADC maps before radical prostatectomy were included in this retrospective study. MRI findings were correlated retrospectively with histopathological results of surgical specimens. Comparisons of ADC values between cancer and noncancer areas were performed with the two-tailed unequal variance t-test. The cutoff ADC level was determined in a way to achieve the best accuracy for detecting prostate cancer. RESULTS: The mean ADC value of all the cancer lesions (n =60) was 1.04 ± 0.31 (×10(-3) mm(2)/s). In the peripheral zone, the mean ADC values of cancer lesions and noncancer areas were 1.07 ± 0.35 and 1.94 ± 0.31, respectively (P < 0.001). In the transition zone, the mean ADC values of cancer lesions and noncancer areas were 1.00 ± 0.22 and 1.56 ± 0.14, respectively (P<0.001). The cutoff level for the ADC value was determined to be 1.35×10(-3) mm(2)/s. It provided sensitivity, specificity, and accuracy of 88%, 96%, and 93%, respectively. CONCLUSION: The cutoff ADC level determined on the basis of the results obtained from radical prostatectomy specimens can help differentiate malignant from nonmalignant lesions.

Perfusion CT is superior to angiography in predicting pancreatic necrosis in patients with severe acute pancreatitis.

BACKGROUND: We performed perfusion computed tomography (P-CT) and angiography of the pancreas in patients with severe acute pancreatitis (SAP) and compared the usefulness of these two methods in predicting the development of pancreatic necrosis. METHODS: We compared P-CT and angiography results taken within 3 days after symptom onset in 21 SAP patients. We divided the pancreas into three areas, the head, body, and tail, and examined each area for perfusion defects (via P-CT) and arterial vasospasms (by angiography). Three weeks later, all patients underwent contrast-enhanced CT to determine whether pancreatic necrosis had developed. RESULTS: Of the 21 SAP patients, 16 exhibited perfusion defects, while 17 proved positive for vasospasms in at least one area. Fourteen patients developed pancreatic necrosis. Of the 63 pancreatic areas from the 21 SAP patients, perfusion defects appeared in 25 areas (39.7%), 24 of which showed vasospasms (96.0%). Angiography showed 33 areas with vasospasms (52.4%), of which 24 showed perfusion defects (72.7%). Of the 25 areas with perfusion defects, 21 developed pancreatic necrosis (84.0%). Of the 33 areas with vasospasms, 21 developed necrosis (63.6%). Pancreatic necrosis developed only in the areas positive both for perfusion defects and for vasospasms. No areas without perfusion defect or vasospasms developed pancreatic necrosis. P-CT predicted the development of pancreatic necrosis with significantly higher accuracy than angiography. CONCLUSION: While both P-CT and angiography are useful in predicting the development of pancreatic necrosis in patients with SAP, P-CT appears to be more accurate for this purpose.

Characterization of atherosclerotic plaque of carotid arteries with histopathological correlation: vascular wall MR imaging vs. color Doppler ultrasonography (US).

PURPOSE: To investigate whether the vessel wall MRI of carotid arteries would differentiate at-risk soft plaque from solid fibrous plaque by identifying liquid components more accurately than color Doppler ultrasonography (US). MATERIALS AND METHODS: This study included 54 carotid arteries in 54 consecutive patients who underwent carotid endarterectomy. MRI was performed using black-blood fat-suppressed (FS) T1-and FS T2-weighted TSE sequences. A total of 68 major segments of the 54 carotid plaques were grouped into four MR categories based on signal intensity index (SII). MR criteria used for the diagnosis of plaque vulnerability were: at-risk soft plaque including a segment of liquid component (category A or B), solid fibrous plaque (category C or D). The MR and US findings were compared with histopathological findings of endarterectomy specimens. RESULTS: Intraoperative findings and microscopic examination of endarterectomy specimens revealed 24 at-risk soft plaques and 30 solid fibrous plaques. The sensitivity, specificity, and accuracy for diagnosing at-risk soft plaque are 96%, 93%, and 94% for MR, and 75%, 63%, and 69% for color Doppler US, respectively. The slice-by-slice MR evaluation of carotid wall also revealed detailed information of plaque segments and correlated well with the features of corresponding histologic sections. CONCLUSION: Vessel wall MRI with MRI category could have a potential to more accurately diagnose an at-risk soft plaque predominantly composed of liquid components in comparison with color Doppler US.

MR imaging features of solid-pseudopapillary tumor of the pancreas.

Solid-pseudopapillary tumor (SPT) of the pancreas is characterized as cystic, necrotic, and hemorrhagic degeneration. In this study, magnetic resonance (MR) findings of 4 cases were reviewed. Patchy or spotty areas of high intensity that suggested hemorrhagic degeneration were constantly detected on fat-suppressed T(1)-weighted images. Dynamic contrast-enhanced MR imaging revealed mild and gradual increase of contrast enhancement in solid portions. Multi-contrast MR imaging that included fat-suppressed T(1)-weighted imaging and dynamic contrast-enhanced imaging allowed accurate diagnosis of SPT and its differentiation from other tumors.

MR imaging of testicular torsion: features of testicular hemorrhagic necrosis and clinical outcomes.

PURPOSE: To determine whether emergency subtraction dynamic contrast-enhanced MR imaging (DCE-MRI) in combination with T2- and T2*-weighted imaging of the testis is useful in the evaluation of patients with testicular torsion. MATERIALS AND METHODS: Fourteen patients with surgically proven testicular torsion were examined using preoperative emergency MRI, including T2-weighted, T2*-weighted, and DCE-MRI. The affected testis was examined histologically in eight patients who underwent orchiectomy, and by postoperative follow-up MRI in six patients who underwent orchiopexy. The diagnostic criteria for testicular torsion and detection of hemorrhagic necrosis in the affected testis in emergency MRI were decreased or no perfusion in DCE-MRI and a spotty and/or streaky pattern of low or very low signal intensity in T2- and T2*-weighted images. The intraoperative findings and clinical outcomes were also compared. RESULTS: The histological findings and follow-up MR images revealed total or partial necrosis of the affected testis in 10 of the 14 patients. In the diagnosis of complete torsion, the sensitivities were 100% for DCE-MRI and 75% for T2- and T2*-weighted imaging. In the detection of testicular necrosis, T2- and T2*-weighted imaging showed the highest accuracy (100%), followed by 12-hour time from onset (93%), intraoperative findings (79%), and DCE-MRI (71%). CONCLUSION: Emergency MRI can help diagnose testicular torsion and detect testicular necrosis when DCE-MRI is used in combination with T2- and T2*-weighted images.

MR imaging of acute biliary disorders.

In patients with acute right-sided epigastric pain, jaundice, and a high fever, it is essential to accurately diagnose the cause of the symptoms, differentiate acute biliary disorders from nonbiliary disorders, and evaluate the severity of the disease. Gray-scale ultrasonography (US) and computed tomography (CT) are useful primary imaging modalities, but their results are not always conclusive. Magnetic resonance (MR) imaging, including MR cholangiopancreatography, can be a valuable complement to US and CT when additional information is needed. MR images have excellent tissue contrast and can provide more specific information, allowing diagnosis of complications that arise from acute cholecystitis, such as empyema, gangrenous cholecystitis, gallbladder perforation, enterocholecystic fistula, emphysematous cholecystitis, and hemorrhagic cholecystitis. In addition, causes of obstructive jaundice, acute suppurative cholangitis, and hemobilia can be clearly demonstrated with multisequence MR imaging. Single-section MR cholangiopancreatography and heavily T2-weighted imaging, in combination with fat-suppressed T1- and T2-weighted imaging, provide comprehensive and detailed information about the biliary system around the obstruction site, biliary calculi, inflammatory processes, purulent material, abscesses, gas, and hemorrhage. Contrast-enhanced MR imaging is useful for evaluation of the gallbladder wall; lack of enhancement and disruption of the wall may be findings specific for gangrenous cholecystitis and gallbladder perforation, respectively.

High-resolution selective three-dimensional magnetic resonance coronary angiography with navigator-echo technique: segment-by-segment evaluation of coronary artery stenosis.

PURPOSE: To investigate the feasibility of high-resolution selective three-dimensional (3D) magnetic resonance coronary angiography (MRCA) in the evaluation of coronary artery stenoses. MATERIALS AND METHODS: In 12 patients with coronary artery stenoses, MRCA of the coronary artery groups, including the coronary segments with stenoses of 50% or greater based on conventional x-ray coronary angiography (CAG), was performed with double-oblique imaging planes by orienting the 3D slab along the major axis of each right coronary artery-left circumflex artery (RCA-LCX) group and each left main trunk-left anterior descending artery (LMT-LAD) group. Ten RCA-LCX and five LMT-LAD MR angiograms were obtained, and the results were compared with those of conventional x-ray angiography. RESULTS: Among 70 coronary artery segments expected to be covered, a total of 49 (70%) segments were fully demonstrated in diagnostic quality. The identification of segmental location of stenoses showed as high an accuracy as 96%. The retrospective analysis for stenosis of 50% or greater yielded the sensitivity, specificity, and accuracy of 80%, 85%, and 84%, respectively. CONCLUSION: Selective 3D MRCA has the potential for segment-by-segment evaluation of major portions of the right and left coronary arteries with high accuracy.

Fast MR imaging in obstetrics.

Ultrasonography (US) is the initial imaging modality of choice for evaluation of patients in obstetrics. However, the results of US are not always sufficient. Magnetic resonance (MR) imaging, which uses no ionizing radiation, may be an ideal method for further evaluation. Although MR imaging is not recommended during the first trimester and use of contrast material is not recommended in pregnant patients, fast MR imaging is useful in various obstetric settings and can provide more specific information with excellent tissue contrast and multiplanar views. In pregnant patients with acute conditions, various diseases (eg, red degeneration of a uterine leiomyoma) may be diagnosed. MR imaging allows characterization of pelvic masses discovered during pregnancy and diagnosis of postpartum complications (eg, abscess, hematoma, ovarian vein thrombosis). In pregnant patients with hydronephrosis, MR urography can demonstrate the site of obstruction and the cause (eg, a ureteral stone). MR pelvimetry may be beneficial in cases of breech presentation. Contrast material-enhanced dynamic MR imaging allows one to evaluate the vascularity of a placental polyp, detect the viable component of a gestational trophoblastic tumor, and diagnose a uterine arteriovenous malformation. MR imaging enables diagnosis of rare forms of ectopic pregnancy and early diagnosis of ectopic pregnancy.