Simple and Green Preparation of Tetraalkoxydiborons and Diboron Diolates from Tetrahydroxydiboron.

Tetraalkoxydiborons can be easily prepared by acid-catalyzed reactions of tetrahydroxydiboron or its anhydride with trialkyl orthoformates. Addition of diols to these reaction mixtures afforded diboron diolates in high yield. In both cases, removal of volatile byproducts is all that is required for the isolation of the diboron. These methods constitute a convenient alternative to previous preparations from tetrakis (dimethylamino) diboron and tetrahydroxydiboron.

Deciphering the Mechanism of Base-Triggered Conversion of Ammonia to Molecular Nitrogen and Methylamine to Cyanide.

We report an in-depth investigation into the ammonia oxidation mechanism by the catalyst [RuIII(tpy)(dmabpy)NH3]3+ ([Ru(NH3)]3+). Stoichiometric reactions of [Ru(NH3)]3+ were carried out with exogenous noncoordinating bases to trigger a proposed redox disproportionation reaction, which was followed using variable-temperature NMR spectroscopy. An intermediate species was identified as a dinitrogen-bridged complex using 15N NMR and Raman spectroscopy on isotopically labeled complexes. This intermediate is proposed to derive from coupling of nitridyl species formed upon sequential redox disproportion reactions. Acetonitrile displaces the dinitrogen bridge to yield free N2. DFT calculations support this lower-energy pathway versus that previously reported for ammonia oxidation by the parent [RuIII(tpy)(bpy)NH3]3+ complex. These experimental and computational results are consistent with the interpretation of redox disproportionation involving sequential hydrogen atom transfer reactions by an amide/aminyl intermediate, [Ru(NH2)-]+ ⇔ [Ru(NH2)•]+, formed upon deprotonation of the parent complex. Control experiments employing a large excess of ammonia as a base indicate this new proposed lower-energy pathway contributes to the oxidation of ammonia to dinitrogen in conditions relevant to electrocatalysis. In addition, analogous methylamine complexes, [Ru(NH2CH3)]2+/3+, were prepared to further test the proposed mechanism. Treating [Ru(NH2CH3)]3+ with a base cleanly yields two products [Ru(NH2CH3)]2+ and [Ru(CN)]+ in an ∼3:1 ratio, fully consistent with the proposed cascade of hydrogen atom transfer reactions by an intermediate.

Risk Factors for Post-ERCP Pancreatitis in Pediatric and Young Adult Patients.

OBJECTIVES: Post-ERCP pancreatitis (PEP) is the most common complication of endoscopic retrograde cholangiopancreatography (ERCP). Limited existing data suggest that prophylactic pancreatic duct (PD) stenting in pediatric patients may increase the risk of PEP. The aim of this study is to identify factors associated with PEP in pediatric patients. METHODS: Patients at a single institution who underwent ERCP between 2012 and 2020 were retrospectively reviewed. Patient and procedure-related factors were collected. Data were analyzed using Chi-square or Fisher exact tests as appropriate and Mann-Whitney-Wilcoxon tests. RESULTS: Seven hundred thirty-six ERCPs were performed for 402 unique patients. Ninety-four cases were complicated by PEP (12.8%), of which 91 were mild and 3 were moderately severe. Pancreatic indication, native major papilla, PD cannulation and injection, and higher American Society for Gastrointestinal Endoscopy (ASGE) complexity were associated with PEP. A higher proportion of patients who received rectal indomethacin (65% vs 47%, P = 0.002), or who had placement of a prophylactic (31% vs 20%, P = 0.01) or therapeutic PD stent (37% vs 27%, P = 0.04) developed PEP; however, in a subgroup analysis of high-risk patients, this association was not persistent. A smaller proportion of PEP patients had PRSS1 mutation compared to non-PEP patients (22% vs 40%, P = 0.04). CONCLUSIONS: This study evaluates factors associated with developing PEP in a large pediatric cohort. A high rate of PEP was observed, likely secondary to higher rates of pancreatic indication and higher ASGE complexity scores compared to previously reported literature. Randomized prospective trials are needed to better define the utility of various interventions.

Systemic Therapy for Resected Pancreatic Adenocarcinoma: How Much is Enough?

BACKGROUND: Systemic therapy is an essential part of treatment for pancreatic ductal adenocarcinoma (PDAC). However, not all patients receive every cycle of chemotherapy and even if they do, the impact of reduced dose density (DD) on survival is not known. PATIENTS AND METHODS: A single institutional prospective database was queried for patients with PDAC who underwent curative resection between 2009 and 2018. The primary outcome was DD, defined as the percentage of total planned chemotherapy actually received and associated survival. RESULTS: Of the 126 patients included, 38.9% underwent a neoadjuvant approach, which was associated with a greater median number of completed chemotherapy cycles (5 cycles versus 4 cycles, p < 0.01) and a higher median total DD (93.0% versus 65.0%, p < 0.01), compared with an adjuvant treatment approach. In both groups, adjuvant chemotherapy completion rates were low, with only 55 patients completing all adjuvant cycles. After sequential survival analysis, patients who received a DD ≥ 80% had improved median overall survival (OS) (27.1 months versus 18.6 months, p = 0.01), compared with patients who achieved a DD < 80%. On multivariate Cox proportional-hazards modeling, only the presence of lymphovascular invasion (HR: 1.77, 95% CI: 1.04-2.99, p = 0.04) and DD < 80% (HR: 1.91, 95% CI: 1.23-3.00, p = 0.01) were associated with decreased OS. CONCLUSIONS: In this cohort study, patients who received ≥ 80% DD had significantly better OS. DD should be considered an important prognostic metric in pancreatic cancer, and strategies are needed to improve chemotherapy tolerance to improve patient outcomes.

Is There a Benefit to Adjuvant Chemotherapy in Resected, Early Stage Pancreatic Ductal Adenocarcinoma?

BACKGROUND: The role of systemic therapy for Stage IA pancreatic ductal adenocarcinoma (PDAC) is unclear. The aim of our study was to evaluate the impact of adjuvant chemotherapy (AC) on survival in patients with early stage disease. METHODS: The National Cancer Database was queried from 2006 to 2017 for resected pT1N0M0 (Stage 1A) PDAC. Exclusion criteria included neoadjuvant therapy, radiation, or those who suffered a 90-day mortality. RESULTS: Of the 1526 patients included in the study, 42.2% received AC and 57.8% underwent surgery alone. Patients who received AC were younger, had fewer comorbidities, and were more likely to have private insurance, compared with those treated with surgery alone. Patients who received AC had longer median overall survival (OS) compared with those who underwent surgery alone (105.7 months vs 72.0 months, p < 0.01). Subset analyses based on individual "good" prognostic features (size ≤ 1.0 cm, lymphovascular invasion negative, well/moderately differentiated, margin negative resection) demonstrated improved OS with AC. Following propensity score matching based on key clinicopathologic features, AC remained associated with improved median OS (83.7 months vs 59.8 months, p < 0.01). However, in the cohort with body/tail tumors (101.2 months vs 95.0 months, p = 0.19) and those with all "good" prognostic features (95.9 months vs 90.6 months, p = 0.15), AC was not associated with improved survival. CONCLUSIONS: In resected, Stage IA PDAC, AC is associated with improved overall survival in the vast majority of patients; however, in select cohorts the role of AC is unclear. Further study is needed to tailor treatment to individual patients with PDAC.

Merging Iridium-Catalyzed C-H Borylations with Palladium-Catalyzed Cross-Couplings Using Triorganoindium Reagents.

A versatile and efficient method to prepare borylated arenes furnished with alkyl, alkenyl, alkynyl, aryl, and heteroaryl functional groups is developed by merging Ir-catalyzed C-H borylations (CHB) with a chemoselective palladium-catalyzed cross-coupling of triorganoindium reagents (Sarandeses-Sestelo coupling) with aryl halides bearing a boronic ester substituent. Using triorganoindium cross-coupling reactions to introduce unsaturated moieties enables the synthesis of borylated arenes that would be difficult to access through the direct application of the CHB methodology. The sequential double catalyzed procedure can be also performed in one vessel.

Recent Advances and Challenges of Electrocatalytic N2 Reduction to Ammonia.

Global ammonia production reached 175 million metric tons in 2016, 90% of which is produced from high purity N2 and H2 gases at high temperatures and pressures via the Haber-Bosch process. Reliance on natural gas for H2 production results in large energy consumption and CO2 emissions. Concerns of human-induced climate change are spurring an international scientific effort to explore new approaches to ammonia production and reduce its carbon footprint. Electrocatalytic N2 reduction to ammonia is an attractive alternative that can potentially enable ammonia synthesis under milder conditions in small-scale, distributed, and on-site electrolysis cells powered by renewable electricity generated from solar or wind sources. This review provides a comprehensive account of theoretical and experimental studies on electrochemical nitrogen fixation with a focus on the low selectivity for reduction of N2 to ammonia versus protons to H2. A detailed introduction to ammonia detection methods and the execution of control experiments is given as they are crucial to the accurate reporting of experimental findings. The main part of this review focuses on theoretical and experimental progress that has been achieved under a range of conditions. Finally, comments on current challenges and potential opportunities in this field are provided.

Amide directed iridium C(sp3)-H borylation catalysis with high N-methyl selectivity.

A bidentate monoanionic ligand system was developed to enable iridium catalyzed C(sp3)-H activation borylation of N-methyl amides. Borylated amides were obtained in moderate to good isolated yields, and exclusive mono-borylation allowed the amide to be the limiting reagent. Selectivity for C(sp3)-H activation was demonstrated in the presence of sterically available C(sp3)-H bonds. Competitive kinetic isotope studies revealed a large primary isotope effect, implicating C-H activation as the rate limiting step.

Homogeneous electrocatalytic oxidation of ammonia to N2 under mild conditions.

We report that ruthenium polypyridyl complexes can catalyze ammonia oxidation to dinitrogen at room temperature and ambient pressure. During bulk electrolysis experiments, gas chromatography and mass spectrometry analysis of the headspace in the electrochemical cell showed that dinitrogen and dihydrogen are generated from ammonia with high faradaic efficiencies. A proposed mechanism where a hydrazine complex is the initial N-N bonded intermediate is supported by chemical and electrochemical experiments. This is a well-defined system for homogeneous electrocatalytic ammonia oxidation. It establishes a platform for answering mechanistic questions relevant to using ammonia to store and distribute renewable energy.

Total pancreatectomy and islet cell autotransplantation: a 10-year update on outcomes and assessment of long-term durability.

BACKGROUND: Total pancreatectomy and islet cell autotransplantation (TPIAT) offers an effective, lasting solution for the management of chronic pancreatitis up to 5-years post-operatively. Our aim was to assess durability of TPIAT at 10-years. METHODS: Patients undergoing TPIAT for chronic pancreatitis eligible for 10-year follow-up were included. Primary outcomes, including endocrine function and narcotic requirements, were reported at 5-, 7.5-, and 10-years post-operatively. RESULTS: Of the 231 patients who underwent TPIAT, 142 met inclusion criteria. All patients underwent successful TPIAT with an average of 5680.3 islet equivalents per body weight. While insulin independence tended to decrease over time (25.7% vs. 16.0% vs. 10.9%, p = 0.11) with an increase in HbA1C (7.6% vs. 8.2% vs. 8.4%, p = 0.09), partial islet function persisted (64.9% vs. 68.0% vs. 67.4%, p = 0.93). Opioid independence was achieved and remained durable in the majority (73.3% vs. 72.2% vs. 75.5%, p = 0.93). Quality of life improvements persisted, with 85% reporting improvement from baseline at 10-years. Estimated median overall survival was 202.7 months. CONCLUSION: This study represents one of the largest series reporting on long-term outcomes after TPIAT, demonstrating excellent long-term pain control and durable improvements in quality of life. Islet cell function declines over time however stable glycemic control is maintained.

One-Pot Iridium Catalyzed C-H Borylation/Sonogashira Cross-Coupling: Access to Borylated Aryl Alkynes.

Borylated aryl alkynes have been synthesized via one-pot iridium catalyzed C-H borylation (CHB)/Sonogashira cross-coupling of aryl bromides. Direct borylation of aryl alkynes encountered problems related to the reactivity of the alkyne under CHB conditions. However, tolerance of aryl bromides to CHB made possible a subsequent Sonogashira cross-coupling to access the desired borylated aryl alkynes.

Para-Selective, Iridium-Catalyzed C-H Borylations of Sulfated Phenols, Benzyl Alcohols, and Anilines Directed by Ion-Pair Electrostatic Interactions.

Para C-H borylations (CHB) of tetraalkylammonium sulfates and sulfamates have been achieved using bipyridine-ligated Ir boryl catalysts. Selectivities can be modulated by both the length of the alkyl groups in the tetraalkylammonium cations and the substituents on the bipyridine ligands. Ion pairing, where the alkyl groups of the cation shield the meta C-H bonds in the counteranions, is proposed to account for para selectivity. The 4,4'-dimethoxy-2,2'-bipyridine ligand gave superior selectivities.

Electronic and Structural Comparisons between Iron(II/III) and Ruthenium(II/III) Imide Analogs.

To examine structural and electronic differences between iron and ruthenium imido complexes, a series of compounds was prepared with different phosphine basal sets. The starting material for the ruthenium complexes was Ru(NAr/Ar*)(PMe3)3 (Ru1/Ru1*), where Ar = 2,6-(iPr)2C6H3 and Ar* = 2,4,6-(iPr)3C6H2, which were prepared from cis-RuCl2(PMe3)4 and 2 equiv of LiNHAr/Ar*. The starting materials for the iron complexes were the analogous Fe(NAr/Ar*)(PMe3)3 species (Fe1/Fe1*), which were not isolated but could be generated in situ from FeCl2, PMe3, and LiNHAr/Ar*. With both iron and ruthenium, the PMe3 starting materials underwent phosphine replacement with chelating ligands to give new group 8 imido complexes in the +2 oxidation state. Addition of 1,2-bis(diphenylphosphino)ethane (dppe) to M1/M1* gave Ru(NAr/Ar*)(PMe3)(dppe) and Fe(NAr/Ar*)(PMe3)(dppe). Addition of 1,2-bis(dimethylphosphino)ethane (dmpe) provided Ru(NAr/Ar*)(dmpe)2. A triphos ligand, {P(Me)2CH2}3SitBu (tP3), was also examined. Addition of tP3 to Fe1 provided Fe(NAr)(tP3) (Fe4), but a similar reaction with Ru1 only gave intractable materials. Oxidation of Fe4 with AgSbF6 gave {Fe(NAr)(tP3)}+SbF6- (Fe4a). Oxidation of Ru2 with AgSbF6 gave the unstable cation {Ru(NAr)(PMe3)(dppe)}+, which dimerized in the presence of acetonitrile via C-C bond formation at the aryl group C4 positions, affording {Ru(NAr)(PMe3)(NCMe)(dppe)}2+. This suggested that there was substantial radical character in the imide π system on oxidation and that an aromatic group substituted at the 4-position might provide greater stability. The cations {Fe(NAr*)(PMe3)(dppe)}+ (Fe2a*), {Ru(NAr*)(PMe3)(dppe)}+ (Ru2a*), and Fe4a were examined by EPR spectroscopy, which suggested differences in electronic structure depending on the metal and ligand set. CASPT2 calculations on model systems for Ru2a* and Fe2a* suggested that the large differences in electronic structure are related to the energy gap between the π-antibonding HOMO and the π-bonding HOMO-1. Both the geometry of the phosphines, which is slightly different between the iron and ruthenium analogs, and the metal center seem to contribute to this energetic difference.

Ir-Catalyzed ortho-Borylation of Phenols Directed by Substrate-Ligand Electrostatic Interactions: A Combined Experimental/in Silico Strategy for Optimizing Weak Interactions.

A strategy for affecting ortho versus meta/para selectivity in Ir-catalyzed C-H borylations (CHBs) of phenols is described. From selectivity observations with ArylOBpin (pin = pinacolate), it is hypothesized that an electrostatic interaction between the partial negatively charged OBpin group and the partial positively charged bipyridine ligand of the catalyst favors ortho selectivity. Experimental and computational studies designed to test this hypothesis support it. From further computational work a second generation, in silico designed catalyst emerged, where replacing Bpin with Beg (eg = ethylene glycolate) was predicted to significantly improve ortho selectivity. Experimentally, reactions employing B2eg2 gave ortho selectivities > 99%. Adding triethylamine significantly improved conversions. This ligand-substrate electrostatic interaction provides a unique control element for selective C-H functionalization.

Does radiologic response correlate to pathologic response in patients undergoing neoadjuvant therapy for borderline resectable pancreatic malignancy?

BACKGROUND AND OBJECTIVES: In patients with borderline resectable pancreas cancers, clinicians frequently consider radiographic response as the primary driver of whether patients should be offered surgical intervention following neoadjuvant therapy (NT). We sought to determine any correlation between radiographic and pathologic response rates following NT. METHODS: Between 2005 and 2015, 38 patients at a tertiary care referral center underwent NT followed by pancreaticoduodenectomy for borderline resectable pancreas cancer. Radiographic response after the completion of NT and pathologic response after surgery were graded according to RECIST and Evans' criteria, respectively. RESULTS: Preoperatively, 50% of patients underwent chemotherapy alone and 50% underwent chemotherapy and chemoradiation. Radiographically, one patient demonstrated a complete radiologic response, 68.4% (n = 26) of patients had stable disease (SD), 26.3% (n = 10) demonstrated a partial response, and one patient had progressive. Among patients without radiographic response, 77.7% (n = 21) achieved a R0 resection. Of patients with SD on imaging, 26.9% (n = 7) had Evans grade IIB or greater pathologic response. CONCLUSIONS: Our data indicate that approximately one-fourth of patients who did not have a radiologic response had a grade IIB or greater pathologic response. In the absence of metastatic progression, lack of radiographic down-staging following NT should not preclude surgery.

Early Recurrence and Omission of Adjuvant Therapy after Pancreaticoduodenectomy Argue against a Surgery-First Approach.

BACKGROUND: Sequencing therapy for patients with periampullary malignancy is controversial. Clinical trial data report high rates of adjuvant therapy completion, though contemporary, real-world rates remain incomplete. We sought to identify patients who failed to receive adjuvant therapy and those at risk for early recurrence (ER) who might benefit most from neoadjuvant therapy (NT). METHODS: We retrospectively reviewed medical records of 201 patients who underwent pancreaticoduodenectomy for periampullary malignancies between 1999 and 2015; patients receiving NT were excluded. Univariate and multivariate analyses were performed to identify predictors of failure to receive adjuvant therapy and ER (within 6 months) as the primary end points. RESULTS: The median age at the time of surgery was 65.5 years (interquartile range 57-74 years). The majority of tumors were pancreatic ductal adenocarcinoma (76.6 %), and 71.6 % of patients received adjuvant therapy after resection. Univariate predictors of failure to undergo adjuvant therapy were advanced age, age-adjusted Charlson comorbidity index, operative transfusion, reoperation, length of stay, and 30- to 90-day readmissions (all p < 0.05). Advanced age, specifically among patients >70 years, persisted as a significant preoperative predictor on multivariate analysis (p < 0.01). Patients who failed to receive adjuvant therapy and/or developed ER had significantly worse overall survival rates compared to all other patients (27.8 vs. 9.7 months; p < 0.01). CONCLUSIONS: Approximately one-third of surgery-first patients undergoing pancreaticoduodenectomy at our institution did not receive adjuvant therapy and/or demonstrated ER. This substantial subset of patients may particularly benefit from NT, ensuring completion of multimodal therapy and/or avoiding futile surgical intervention.

Harnessing C-H Borylation/Deborylation for Selective Deuteration, Synthesis of Boronate Esters, and Late Stage Functionalization.

Ir-catalyzed deborylation can be used to selectively deuterate aromatic and heteroaromatic substrates. Combined with the selectivities of Ir-catalyzed C-H borylations, uniquely labeled compounds can be prepared. In addition, diborylation/deborylation reactions provide monoborylated regioisomers that complement those prepared by C-H borylation. Comparisons between Ir-catalyzed deborylations and Pd-catalyzed deborylations of diborylated indoles described by Movassaghi are made. The Ir-catalyzed process is more effective for deborylating aromatics and is generally more effective in the monodeborylation of diborylated thiophenes. These processes can be applied to complex molecules such as clopidogrel.

Total pancreatectomy with islet cell autotransplantation as the initial treatment for minimal-change chronic pancreatitis.

OBJECTIVES: Patients with minimal-change chronic pancreatitis (MCCP) are traditionally managed medically with poor results. This study was conducted to review outcomes following total pancreatectomy with islet cell autotransplantation (TP/IAT) as the initial surgical procedure in the treatment of MCCP. METHODS: All patients submitted to TP/IAT for MCCP were identified for inclusion in a single-centre observational study. A retrospective chart review was performed to identify pertinent preoperative, perioperative and postoperative data. RESULTS: A total of 84 patients with a mean age of 36.5 years (range: 15-60 years) underwent TP/IAT as the initial treatment for MCCP. The most common aetiology of chronic pancreatitis in this cohort was idiopathic (69.0%, n = 58), followed by aetiologies associated with genetic mutations (16.7%, n = 14), pancreatic divisum (9.5%, n = 8), and alcohol (4.8%, n = 4). The most common genetic mutations pertained to CFTR (n = 9), SPINK1 (n = 3) and PRSS1 (n = 2). Mean ± standard error of the mean preoperative narcotic requirements were 129.3 ± 18.7 morphine-equivalent milligrams (MEQ)/day. Overall, 58.3% (n = 49) of patients achieved narcotic independence and the remaining patients required 59.4 ± 10.6 MEQ/day (P < 0.05). Postoperative insulin independence was achieved by 36.9% (n = 31) of patients. The Short-Form 36-Item Health Survey administered postoperatively demonstrated improvement in all tested quality of life subscales. CONCLUSIONS: The present report represents one of the largest series demonstrating the benefits of TP/IAT in the subset of patients with MCCP.

Silyl phosphorus and nitrogen donor chelates for homogeneous ortho borylation catalysis.

Ir catalysts supported by bidentate silyl ligands that contain P- or N-donors are shown to effect ortho borylations for a range of substituted aromatics. The substrate scope is broad, and the modular ligand synthesis allows for flexible catalyst design.

Long-term outcomes after total pancreatectomy and islet cell autotransplantation: is it a durable operation?

OBJECTIVE: Total pancreatectomy and islet cell autotransplantation (TPIAT) has been increasingly utilized for the management of chronic pancreatitis (CP) with early success. However, the long-term durability of this operation remains unclear. METHODS: All patients undergoing TPIAT for the treatment of CP with 5-year or greater follow-up were identified for inclusion in this single-center observational study. End points included narcotic requirements, glycemic control, islet function, quality of life (QOL), and survival. RESULTS: Between 2000 and 2013, 166 patients underwent TPIAT; 112 of these patients had 5-year follow-up data to analyze. All patients underwent successful IAT with a mean of 6027 ± 595 islet equivalents per body weight. There was no perioperative mortality and actuarial survival at 5 years was 94.6%. The narcotic independence rate at 1 year was 55% and continued to improve to 73% at 5-year follow-up (P < 0.05). The insulin independence rate declined over time (38% at 1 year vs 27% at more than 5 years), but insulin requirements remained similar (21.4 vs 24.3 units per day, P = 0.6). All patients achieved stable glycemic control with a median hemoglobin A1C (HgA1C) of 6.9% (range: 5.85%-8.3%). The short form 36-item QOL assessment of a subset of patients available for contact demonstrated continued improvements in all tested modules in patients with at least 5-year follow-up. Two patients developed diabetic complications requiring whole organ pancreas transplant for salvage. CONCLUSIONS: This represents one of the largest series examining long-term outcomes after TPIAT. This operation produces durable pain relief and improvement in QOL parameters. Insulin independence rates decline over time, but most patients maintain stable glycemic control.