Your browser doesn't support javascript.
loading
Show: 20 | 50 | 100
Results 1 - 20 de 34
Filter
1.
Radiol Case Rep ; 19(10): 4138-4141, 2024 Oct.
Article in English | MEDLINE | ID: mdl-39114863

ABSTRACT

A 60-year-old female with a BRCA2 mutation and a history of breast cancer presented with diffuse abdominal pain and elevated liver enzymes. Imaging revealed a porta-hepatis mass, prompting consideration of hilar cholangiocarcinoma or breast cancer metastasis. Further investigation including biopsy and 18F-fluorodeoxyglucose positron emission tomography/computed tomography findings were inconsistent with malignancy, leading to investigation of non-neoplastic causes. Elevated IgG4 levels suggested IgG4-related disease, a mass-forming fibroinflammatory condition. This case demonstrates IgG4-related disease exclusively impacting the portal vein and underscores the importance of considering IgG4-related disease in the differential diagnosis of hepatic masses.

2.
Endosc Ultrasound ; 12(3): 334-341, 2023.
Article in English | MEDLINE | ID: mdl-37693114

ABSTRACT

Background and Objectives: Prospective studies comparing EUS-guided liver biopsy (EUS-LB) to percutaneous LB (PC-LB) are scarce. We compared the efficacy and safety of EUS-LB with those of PC-LB in a prospective randomized clinical trial. Methods: Between 2020 and 2021, patients were enrolled and randomized (1:1 ratio). The primary outcome was defined as the proportion of patients with ≥11 complete portal tracts (CPTs). The sample size (n = 80) was calculated based on the assumption that 60% of those in the EUS-LB and 90% of those in the PC-LB group will have LB with ≥11 CPTs. The secondary outcomes included proportion of patients in whom a diagnosis was established, number of CPTs, pain severity (Numeric Rating Scale-Pain Intensity), duration of hospital stay, and adverse events. Results: Eighty patients were enrolled (median age, 53 years); 67.5% were female. Sixty percent of those in the EUS-LB and 75.0% of those in the PC-LB group met the primary outcome (P = 0.232). The median number of CPTs was higher in the PC-LB (17 vs 13; P = 0.031). The proportion of patients in whom a diagnosis was established was similar between the groups (92.5% [EUS-LB] vs 95.0% [PC-LB]; P = 1.0). Patients in the EUS-LB group had less pain severity (median Numeric Rating Scale-Pain Intensity, 2.0 vs 3.0; P = 0.003) and shorter hospital stay (2.0 vs 4.0 hours; P < 0.0001) compared with the PC-LB group. No patient experienced a serious adverse event. Conclusions: EUS-guided liver biopsy was safe, effective, better tolerated, and associated with a shorter hospital stay.

4.
Radiol Case Rep ; 17(11): 4064-4068, 2022 Nov.
Article in English | MEDLINE | ID: mdl-36065242

ABSTRACT

Renal cryoablation (CA) has become an accepted treatment option for patients with small renal tumors and co-morbidities that make them less favorable for surgical intervention. Complications from renal CA have been previously reported and are generally associated with increasing size and central location of the tumor. Ureteral injury from renal CA, although rare, can be difficult to manage and may require complex surgeries in patients who are poor surgical candidates to begin with. We report a case of a renal mass CA complicated by proximal ureteral necrosis and transection, treated with multiple minimally invasive procedures ultimately resulting in successful bridging of the necrotic segment with nephroureteral stent and thus avoiding major surgery.

5.
J Investig Med High Impact Case Rep ; 10: 23247096211070388, 2022.
Article in English | MEDLINE | ID: mdl-35045737

ABSTRACT

Hemosuccus pancreaticus is a rare but potentially torrential and life-threatening cause of acute upper gastrointestinal bleeding. It is described as an intermittent hemorrhage from the major duodenal papilla via the main pancreatic duct. Peripancreatic pseudoaneurysm following chronic pancreatitis is a common underlying etiology. However, gastroduodenal artery pseudoaneurysm-related hemosuccus pancreaticus remains exceedingly rare in the etiological spectrum of upper gastrointestinal bleeding. We hereby delineate a rare case of hemosuccus pancreaticus associated with gastroduodenal artery pseudoaneurysm in a patient who initially presented with abdominal pain and hematochezia. He was successfully managed with coil embolization without recurrence or sequelae. Furthermore, we conducted a search of the MEDLINE (PubMed and Ovid) database for relevant studies on hemosuccus pancreaticus published between inception and September 15, 2021. The available clinical evidence on causes, presentation patterns, diagnosis, and management was analyzed and summarized. This article highlights the rarity, the intermittent nature of hemorrhage, and the lack of a standardized diagnostic approach for this elusive disease. Clinicians should remain cognizant of hemosuccus pancreaticus, especially in patients presenting with symptoms and signs of intermittent gastrointestinal bleeding and abdominal pain. Prompt diagnosis carries paramount importance in saving patients from repeat hospital admissions and disease-associated morbidity and mortality. Conventional angiography with coil embolization may constitute an effective treatment strategy.


Subject(s)
Ampulla of Vater , Aneurysm, False , Pancreatitis, Chronic , Aneurysm, False/diagnostic imaging , Aneurysm, False/etiology , Gastrointestinal Hemorrhage/etiology , Gastrointestinal Hemorrhage/therapy , Humans , Male , Pancreatic Ducts
6.
ACS Nano ; 15(12): 19956-19969, 2021 12 28.
Article in English | MEDLINE | ID: mdl-34797988

ABSTRACT

In vivo multiplexed imaging aims for noninvasive monitoring of tumors with multiple channels without excision of the tissue. While most of the preclinical imaging has provided a number of multiplexing channels up to three, Raman imaging with surface-enhanced Raman scattering (SERS) nanoparticles was suggested to offer higher multiplexing capability originating from their narrow spectral width. However, in vivo multiplexed SERS imaging is still in its infancy for multichannel visualization of tumors, which require both sufficient multiplicity and high sensitivity concurrently. Here we create multispectral palettes of gold multicore-near-infrared (NIR) resonant Raman dyes-silica shell SERS (NIR-SERRS) nanoparticle oligomers and demonstrate noninvasive and five-plex SERS imaging of the nanoparticle accumulation in tumors of living mice. We perform the five-plex ratiometric imaging of tumors by varying the administered ratio of the nanoparticles, which simulates the detection of multiple biomarkers with different expression levels in the tumor environment. Furthermore, since this method does not require the excision of tumor tissues at the imaging condition, we perform noninvasive and longitudinal imaging of the five-color nanoparticles in the tumors, which is not feasible with current ex vivo multiplexed tissue analysis platforms. Our work surpasses the multiplicity limit of previous preclinical tumor imaging methods while keeping enough sensitivity for tumor-targeted in vivo imaging and could enable the noninvasive assessment of multiple biological targets within the tumor microenvironment in living subjects.


Subject(s)
Metal Nanoparticles , Nanoparticles , Neoplasms , Animals , Diagnostic Imaging , Gold , Mice , Neoplasms/diagnostic imaging , Spectrum Analysis, Raman , Tumor Microenvironment
7.
Radiol Case Rep ; 16(5): 1227-1232, 2021 May.
Article in English | MEDLINE | ID: mdl-33815646

ABSTRACT

Recurrent or metastatic peri-urethral pelvic malignancies are a difficult-to-treat entity. Re-resection is recommended when possible but is frequently unfavorable due to scar tissue, fibrosis, and obliteration of tissue planes following previous interventions such as surgical resection and/or radiation therapy. Curative options for patients that have unresectable cancer are limited. Cryo-ablation has been extensively studied in the treatment of unresectable renal, liver and lung malignancies and has the potential to provide definitive treatment for recurrent pelvic malignancy. There is a paucity of reports of salvage cryo-ablation in patients with recurrent pelvic malignancies, as most of these tumors are located close to critical structures that could be irreversibly injured by thermal ablation and are hence treated with some form of radiation therapy. But, for patients who fail surgical and radiation treatments, options are limited. Here, we describe two cases of regional tumor recurrence in the pelvis treated with percutaneous cryoablation using protective techniques to avoid thermal injury to adjacent structures. In each case, cryo-ablation was performed successfully despite extensive previous surgical and radiation interventions. Salvage cryo-ablation resulted in a positive clinical and imaging response with an improvement in quality of life and absence of recurrence on follow-up imaging which continues to persist at the writing of this manuscript about 8 and 12-months following treatment.

9.
AJR Am J Roentgenol ; 217(3): 676-690, 2021 09.
Article in English | MEDLINE | ID: mdl-32966117

ABSTRACT

Pain is a complex syndrome that is difficult to treat. The increasing numbers of patients living with chronic diseases has led to increasing pain management needs and the rise of opioid use disorder (OUD) as a major and potentially lethal public health concern. Treatment of chronic pain with prescription opioids alone is not always successful, and a multidisciplinary approach is paramount to address the needs of patients at risk of developing or suffering from OUD. Interventional radiologists trained to perform minimally invasive procedures with negligible downtime and postprocedure pain can help stem the tide of opioid-related deaths and disability. This article reviews a wide range of minimally invasive procedures, including vertebral augmentation, sacroplasty, thermal ablation of osseous metastasis, nerve blocks, and gonadal vein embolization, that interventional radiologists are now using successfully to treat chronic pain. The evidence to support use of such procedures is highlighted. This article also briefly discusses emerging techniques such as arterial embolization and ablation for knee and shoulder osteoarthritis that have not yet been fully tested but exhibit strong potential in chronic pain management. By reducing opioid use in patients suffering from chronic pain, these minimally invasive procedures can potentially prevent escalation to OUD.


Subject(s)
Ablation Techniques/methods , Chronic Pain/therapy , Embolization, Therapeutic/methods , Nerve Block/methods , Pain Management/methods , Radiology, Interventional/methods , Chronic Pain/diagnostic imaging , Humans
10.
J Clin Imaging Sci ; 10: 54, 2020.
Article in English | MEDLINE | ID: mdl-33024609

ABSTRACT

OBJECTIVES: Percutaneous renal biopsy (PRB) plays a critical role in the work-up of renal parenchymal disease. Although it is considered a low-risk procedure, additional interventions may be required in about 7% of the cases following biopsy. The purpose of this study was to identify risk factors for major hemorrhage by microscopic analysis of the cores obtained following PRB, with an intent to enhance the sensitivity and specificity of the risk stratification process, especially in patients undergoing this procedure in an outpatient setting. MATERIAL AND METHODS: A retrospective review identified 17 of 179 patients (9.50%) with major hemorrhage following PRB between July 2014 and June 2019. Using propensity score matching, 26 controls (without major hemorrhage) were matched to 17 cases (with major hemorrhage). The biopsy cores obtained from the cases and controls were analyzed by a single pathologist for medullary, cortical, total (medullary + cortical) lengths, and the number of arcuate arteries (AAs). Medullary:cortical (M:C), cortical:total (C:T), and medullary:total (M:T) length ratios were then calculated. RESULTS: A stratified version of logistic regression was used to test for an association between each of the variables identified on the cores and the probability of a major hemorrhage. The analysis revealed that there was a statistically significant association between the number of AAs per specimen with the risk of major hemorrhage (P = 0.0006). When 0, 1, or >2 AAs were identified, the frequency of major hemorrhage was 13.04%, 66.67%, and 75.00%, respectively. The odds of major hemorrhage were 6 times higher with one AA and (95% CI, 1.28-32.30) and 15 times higher with >2 AAs (95% CI, 1.41-169.57). No significant association was found between medullary length (P = 0.228), medulla:cortex (M:C) (P = 0.089), medulla:total (M:T) (P = 0.108), or cortex:total (C:T) (P = 0.112) length ratios and major hemorrhage. CONCLUSION: There was a strong and incremental correlation between major renal hemorrhage following PRB and the number of AAs per core specimen. Identification of AAs by the pathologist, while assessing for sample adequacy, in the US suite can help predict major hemorrhage in patients undergoing PRBs.

11.
Diagn Interv Radiol ; 26(5): 464-469, 2020 Sep.
Article in English | MEDLINE | ID: mdl-32755878

ABSTRACT

PURPOSE: The role of computed tomography (CT)-guided gastrostomy tube placement is still evolving. It is a valuable alternative to guide gastrostomy tube placement in a few selected patients, who are not candidates for the established endoscopy- or fluoroscopy-guided gastrostomy tube placement. Our objective was to describe our institutional experience placing gastrostomy tubes using CT guidance and to conduct a review of literature for similar studies to provide the best current evidence on success rates and complications. METHODS: We identified gastrostomy tubes placed under CT guidance at our institution using a comprehensive case log. We also identified studies in the literature, through a systematic search of PubMed. In both the local and literature analyses, we recorded success and complication rates. RESULTS: A total of 31 patients underwent 33 attempted CT-guided gastrostomy tube placements at our institution, with 32 successful procedures yielding a success rate of 97%. The overall rate of successful gastrostomy tube placement using CT-guidance was 94.9% (634/668), as reported in the existing literature. CONCLUSION: CT-guidance is an effective method for gastrostomy tube placement and may play an important role in patients for whom endoscopic or fluoroscopic gastrostomy tube placement is not feasible.


Subject(s)
Gastrostomy , Tomography, X-Ray Computed , Catheterization , Fluoroscopy , Humans , Retrospective Studies
12.
Radiol Case Rep ; 15(8): 1359-1365, 2020 Aug.
Article in English | MEDLINE | ID: mdl-32636973

ABSTRACT

Liver metastases in cervical cancer is rare and can be difficult-to-treat. The current guidelines established by the Gynecologic Oncology Group recommend platinum-based systemic chemotherapy in combination with an anti-angiogenic agent such as bevacizumab, however, overall survival remains poor following diagnosis and options for patients who fail chemotherapy are limited. Yttrium-90 (Y90) radioembolization (RE) has shown great promise in the treatment of chemo-refractory colorectal liver metastases. We describe a 30-year-old female with a history of stage IB endocervical adenocarcinoma who later developed metastases to the liver, that were unresponsive to multiple chemotherapeutics and chemoembolization, and was successfully treated with Y90 RE with concurrent systemic Pembrolizumab. The Y90 RE treatment resulted in positive clinical and imaging responses with improvement in her quality of life, all of which continue to persist at the time of writing this manuscript about 8-months into her RE treatment.

13.
Radiol Case Rep ; 15(8): 1149-1154, 2020 Aug.
Article in English | MEDLINE | ID: mdl-32528603

ABSTRACT

Persistent eating of non-nutritive, nonfood substances (Pica) is seen in children and adult patients with psychiatric problems. Ingestion of multiple metallic FBs with resultant bezoar formation is rare. While many FBs are passed without complication, mucosal injury, bleeding, obstruction or perforation can occur in some cases. Endoscopic FB removal is performed in 20% of patients following FB ingestion. Generally, these are safe procedures, and very effective in extracting ingested FBs. We report, a 25-year-old male patient with a metal ingestion predominant Pica, requiring multiple prior extraction procedures (including open gastrostomy). He developed a splenic artery pseudoaneurysm following his latest endoscopic FB removal, that was successfully treated with transarterial coil embolization. The unique circumstances leading to this rare complication and its successful endovascular management make this case worthy of report.

14.
Radiol Case Rep ; 15(8): 1197-1201, 2020 Aug.
Article in English | MEDLINE | ID: mdl-32550958

ABSTRACT

Bladder cancer (BC) is a relatively common tumor, with a male preponderance. High-grade muscle invasive bladder cancer (MIBC) has a very high incidence of pelvic lymph node metastasis at presentation. Involvement of the retro-crural lymph nodes, although has been described in other pelvic tumors, is very uncommon for BC. Cryoablation in the retro-crural region is extremely challenging due to the proximity to the critical structures like inferior venacava and aorta and has not been extensively reported. We describe a 56-year old male patient with MIBC who underwent extensive treatments including radical cystoprostatectomy, chemoradiation and immunotherapy, ultimately with localized disease in the retro-crural region. Single session cryoablation of these lymph nodes was performed with a curative intent yielding a positive response that has persisted for more than 2 years.

15.
J Clin Imaging Sci ; 10: 33, 2020.
Article in English | MEDLINE | ID: mdl-32547836

ABSTRACT

OBJECTIVES: Over 25% of the high-risk population screened for lung cancer have an abnormal computed tomography (CT) scan. Conventionally, these lesions have been biopsied with CT guidance with a high diagnostic yield. Electromagnetic navigational bronchoscopy (ENB) with transbronchial biopsy has emerged as a technology that improves the diagnostic sensitivity of conventional bronchoscopic biopsy. It has been used to biopsy lung lesions, due to the low risk of pneumothorax. It is, however, a new technology that is expensive and its role in the diagnosis of the solitary pulmonary nodule (SPN) is yet to be determined. The purpose of this study was to evaluate the diagnostic yield of CT-guided biopsy (CTB) following non-diagnostic ENB biopsy and identify characteristics of the lesion that predicts a low diagnostic yield with ENB, to ensure appropriate use of ENB in the evaluation of SPN. MATERIALS AND METHODS: One hundred and thirty-five lung lesions were biopsied with ENB from January 2017 to August 2019. Biopsies were considered diagnostic if pathology confirmed malignancy or inflammation in the appropriate clinical and imaging setting. We evaluated lesions for several characteristics including size, lobe, and central/peripheral distribution. The diagnostic yield of CTB in patients who failed ENB biopsies was also evaluated. Logistic regression was used to identify factors likely to predict a non-diagnostic ENB biopsy. RESULT: Overall, ENB biopsies were performed in 135 patients with solitary lung lesions. ENB biopsies were diagnostic in 52% (70/135) of the patients. In 23 patients with solitary lung lesions, CTBs were performed following a non-diagnostic ENB biopsy. The CTBs were diagnostic in 87% of the patients (20/23). ENB biopsies of lesions <21.5 mm were non-diagnostic in 71% of cases (42/59); 14 of these patients with non-diagnostic ENB biopsies had CTBs, and 86% of them were diagnostic (12/14). ENB biopsies of lesions in the lower lobes were non- diagnostic in 59% of cases (35/59); 12 of these patients with non-diagnostic ENB biopsies had CTBs, and 83% were diagnostic (10/12). ENB biopsies of lesions in the outer 2/3 were non-diagnostic in 57% of cases (50/87); 21 of these patients with non-diagnostic ENB biopsies had CTBs, and 86% were diagnostic (18/21). CONCLUSION: CTBs have a high diagnostic yield even following non-diagnostic ENB biopsies. Lesions <21.5 mm, in the outer 2/3 of the lung, and in the lower lung have the lowest likelihood of a diagnostic yield with ENB biopsies. Although CTBs have a slightly higher pneumothorax rate, these lesions would be more successfully diagnosed with CTB as opposed to ENB biopsy, in the process expediting the diagnosis and saving valuable medical resources.

16.
Indian J Radiol Imaging ; 29(3): 313-317, 2019.
Article in English | MEDLINE | ID: mdl-31741602

ABSTRACT

Ectopic varices are complex and highly variable entities that are not fully understood. Duodenal varices from pancreatitis have rarely been reported. Ectopic varices have much higher bleeding rates than the more common gastro-esophageal varices, and are associated with higher mortality. The ideal management of this difficult problem is not only to ensure prompt hemostasis, but also address the etiology or hemodynamics of the ectopic varices. We discuss the endovascular management of bleeding duodenal varices, which developed from superior mesenteric vein occlusion, following repeated attacks of pancreatitis. This unusual case was managed by a multidisciplinary collaborative approach between the gastrointestinal service and Interventional radiology. The classification system for ectopic varices and management options has been discussed in some detail. Medium term follow-up (8 months), at the time of this writing, showed that the patient is doing well, without interval hematemesis, imaging findings of recurrent/new varices or stent occlusion.

17.
World J Radiol ; 11(9): 116-125, 2019 Sep 28.
Article in English | MEDLINE | ID: mdl-31608143

ABSTRACT

BACKGROUND: Primary appendiceal cancers are rare, and they generally present with liver and/or peritoneal metastases. Currently there are no guidelines to treat metastatic appendiceal cancer, and hence they are treated as metastatic colorectal cancer. Combining Yttrium 90 (Y-90) radioembolization (RE) with systemic chemotherapy early in the treatment of right sided colon cancers has been shown to improve survival. Based on this data, a combination of systemic chemotherapy and Y-90 RE was used to treat a case of metastatic appendiceal cancer. CASE SUMMARY: A 76-year-old male presented to the emergency room with progressive right lower quadrant pain. A Computed Tomography of the abdomen and pelvis was performed which showed acute appendicitis and contained perforation. Urgent laparoscopic appendectomy was then followed by histological analysis, which was significant for appendiceal adenocarcinoma. After complete workup he underwent right hemicolectomy and lymph node dissection. He received adjuvant chemotherapy as the local lymph nodes were positive. Follow-up imaging was significant for liver metastasis. Due to rapid growth of the liver lesions and new peritoneal nodules, the patient was treated with a combination of Y-90 RE and folinic acid, fluorouracil, and irinotecan with bevacizumab and not microwave ablation as previously planned. Follow up imaging demonstrated complete response of the liver lesions. At 12-mo follow-up, the patient continued to enjoy good quality of life with no recurrent disease. CONCLUSION: Utilization of Y-90 RE concomitantly with systemic chemotherapy early in the treatment of appendiceal cancer may provide improved control of this otherwise aggressive cancer.

18.
ACS Nano ; 13(3): 2858-2869, 2019 03 26.
Article in English | MEDLINE | ID: mdl-30714717

ABSTRACT

Nanoparticles' enhanced permeation and retention (EPR) variations due to tumor heterogeneity in naturally occurring brain tumors are commonly neglected in preclinical nanomedicine studies. Recent pathological studies have shown striking similarities between brain tumors in humans and dogs, indicating that canine brain tumors may be a valuable model to evaluate nanoparticles' EPR in this context. We recruited canine clinical cases with spontaneous brain tumors to investigate nanoparticles' EPR in different brain tumor pathologies using surface-enhanced Raman spectroscopy (SERS). We used gold nanoparticles due to their surface plasmon effect that enables their sensitive and microscopic resolution detection using the SERS technique. Raman microscopy of the resected tumors showed heterogeneous EPR of nanoparticles into oligodendrogliomas and meningiomas of different grades, without any detectable traces in necrotic parts of the tumors or normal brain. Raman observations were confirmed by scanning electron microscopy (SEM) and X-ray elemental analyses, which enabled localization of individual nanoparticles embedded in tumor tissues. Our results demonstrate nanoparticles' EPR and its variations in clinically relevant, spontaneous brain tumors. Such heterogeneities should be considered alongside routine preoperative imaging and histopathological analyses in order to accelerate clinical management of brain tumors using nanomedicine approaches.


Subject(s)
Brain Neoplasms/chemistry , Brain Neoplasms/diagnostic imaging , Nanomedicine , Nanoparticles/chemistry , Animals , Blood Chemical Analysis , Brain Neoplasms/surgery , Dogs , Gold/chemistry , Magnetic Resonance Imaging , Particle Size , Silicon Dioxide/chemistry , Surface Properties
19.
ACS Nano ; 13(2): 1354-1364, 2019 02 26.
Article in English | MEDLINE | ID: mdl-30624916

ABSTRACT

Cancers of the gastrointestinal (GI) tract are among the most frequent and most lethal cancers worldwide. An important reason for this high mortality is that early disease is typically asymptomatic, and patients often present with advanced, incurable disease. Even in high-risk patients who routinely undergo endoscopic screening, lesions can be missed due to their small size or subtle appearance. Thus, current imaging approaches lack the sensitivity and specificity to accurately detect incipient GI tract cancers. Here we report our finding that a single dose of a high-sensitivity surface-enhanced resonance Raman scattering nanoparticle (SERRS-NP) enables reliable detection of precancerous GI lesions in animal models that closely mimic disease development in humans. Some of these animal models have not been used previously to evaluate imaging probes for early cancer detection. The studies were performed using a commercial Raman imaging system, a newly developed mouse Raman endoscope, and finally a clinically applicable Raman endoscope for larger animal studies. We show that this SERRS-NP-based approach enables robust detection of small, premalignant lesions in animal models that faithfully recapitulate human esophageal, gastric, and colorectal tumorigenesis. This method holds promise for much earlier detection of GI cancers than currently possible and could lead therefore to marked reduction of morbidity and mortality of these tumor types.


Subject(s)
Endoscopy/methods , Gastrointestinal Neoplasms/diagnosis , Gastrointestinal Tract/metabolism , Nanoparticles/chemistry , Spectrum Analysis, Raman/methods , Animals , Disease Models, Animal , Male , Mice , Mice, Inbred C57BL , Mice, Knockout
20.
Organometallics ; 38(17): 3377-3387, 2019 Sep 09.
Article in English | MEDLINE | ID: mdl-32565607

ABSTRACT

Aryl carbonates, a common protecting group in synthetic organic chemistry, are potentially valuable electrophiles in cross-coupling reactions. Here, after performing a thorough evaluation of different precatalysts, we demonstrate that (dcypf)Ni(2-ethylphenyl)(Br) (dcypf = 1,1-bis-(dicyclohexylphosphino)ferrocene) is an efficient precatalyst for Suzuki-Miyaura reactions using a variety of aryl carbonates as substrates. Mechanistic studies indicate that (dcypf)Ni(2-ethylphenyl)(Br), which contains a bidentate phosphine that binds in a trans geometry, is an effective precatalyst for these reactions for two reasons: (i) it rapidly forms the Ni(O) active species and (ii) it minimizes comproportionation reactions between the Ni(O) active species and both the unactivated Ni(II) precatalyst and on-cycle Ni(II) complexes to form catalytically inactive Ni(I) species. In contrast, the state of the art precatalyst (dppf)Ni(o-tolyl)(Cl) (dppf = 1,1-bis(diphenylphosphino)ferrocene), which contains a bidentate phosphine that binds in a cis geometry, forms Ni(I) species during activation and is essentially inactive for aryl carbonate couplings. Although the exact reasons on a molecular level why the dcypf system is more active than the dppf system are unclear, our results indicate that in general Ni catalysts supported by the dcypf ligand will give better performance for catalytic reactions involving substrates which undergo relatively slow oxidative addition, such as aryl carbonates.

SELECTION OF CITATIONS
SEARCH DETAIL