Reactivity of Diruthenium Bisborylene Complexes: Formation of B-C and B-H Bonds via Borylene Ligand Coupling.

Thermal or photoinduced isomerization of diruthenium bridging bisborylene complexes [{Cp*(H)2Ru}2(µ-BAr)2] (1a, Ar = Ph; 1b, Ar = 3,4,5-F3C6H2) led to nido-ruthenacarboranes 2a and 2b with newly formed B-C and B-H bonds. The reaction mechanism was analyzed by deuterium-labeling experiments and density functional theory calculations. Additionally, 2-fold B-H coupling between borylene and two hydrido ligands of 1a can be achieved, assisted by Lewis base IPr2Me2 to generate a dinuclear bridging borylene complex [(Cp*Ru)2(µ-H)2(µ-BPh)] (3). Our results provide new reactivity patterns for borylene-based functionalizations.

Bifunctional Ligand Enables Gold-Catalyzed Propargyl C-H Functionalization via Reactive Gold Allenylidene Intermediate.

Gold allenylidene species have been seldom exploited as reactive intermediates in synthetically versatile catalytic reactions. By employing alkynylbenziodoxoles as the substrates and bifunctional WangPhos as the metal ligand, this work demonstrated ready catalytic access to these intermediates of general substitution patterns and their electrophilic reactivities at the γ-carbon center with a diverse range of nucleophiles. The reaction is driven by the reductive decomposition of the benziodoxole moiety and achieves the replacement of a propargylic proton with an N/O/C-based nucleophile, hence realizing reactivity umpolung. Corroborated by Density Functional Theory (DFT) calculations, the reaction mechanism involves a mild propargylic deprotonation. In contrast to prior works employing a tertiary amine functionality, a weakly BrØnsted-basic amide group in WangPhos is surprisingly effective in deprotonation at the propargylic position under a gold-ligand cooperation regime.

Directed SN2 Glycosylation Employing an Amide-Functionalized 1-Naphthoate Platform Featuring a Selectivity-Safeguarding Mechanism.

This work implements a catalytic SN2 glycosylation by employing an amide-functionalized 1-naphthoate platform as a latent glycosyl leaving group. Upon gold-catalyzed activation, the amide group enables the SN2 process by directing the attack of the glycosyl acceptor via H-bonding interaction, which results in stereoinversion at the anomeric center. Unique in this approach is that the amide group also enables a novel safeguarding mechanism by trapping oxocarbenium intermediates and, hence, minimizing stereorandom SN1 processes. The strategy is applicable to the synthesis of a broad range of glycosides with high to excellent levels of stereoinversion from anomerically pure/enriched glycosyl donors. These reactions are generally high-yielding, and their applications in the synthesis of challenging 1,2-cis-linkage-rich oligosaccharides are demonstrated.

Reactivities of α-Oxo BMIDA Gold Carbenes Generated by Gold-Catalyzed Oxidation of BMIDA-Terminated Alkynes.

An oxidative strategy is reported to access α-oxo BMIDA gold carbenes directly from BMIDA-terminated alkynes. Besides offering expedient access to seldom studied boryl metal carbenes, these BMIDA gold carbene species undergo facile insertions into methyl, methylene, methine, and benzylic C-H bonds in the absence of the Thorpe-Ingold effect. They also undergo efficient OH insertion, cyclopropanation, and F-C alkylations. This chemistry provides rapid access to structurally diverse α-BMIDA ketones, which are scarcely documented. In combination with DFT studies, the role of BMIDA is established to be an electron-donating group that attenuates the high electrophilicity of the gold carbene center.

Diastereoselective Synthesis of Aryl C-Glycosides from Glycosyl Esters via C-O Bond Homolysis.

C-aryl glycosyl compounds offer better in vivo stability relative to O- and N-glycoside analogues. C-aryl glycosides are extensively investigated as drug candidates and applied to chemical biology studies. Previously, C-aryl glycosides were derived from lactones, glycals, glycosyl stannanes, and halides, via methods displaying various limitations with respect to the scope, functional-group compatibility, and practicality. Challenges remain in the synthesis of C-aryl nucleosides and 2-deoxysugars from easily accessible carbohydrate precursors. Herein, we report a cross-coupling method to prepare C-aryl and heteroaryl glycosides, including nucleosides and 2-deoxysugars, from glycosyl esters and bromoarenes. Activation of the carbohydrate substrates leverages dihydropyridine (DHP) as an activating group followed by decarboxylation to generate a glycosyl radical via C-O bond homolysis. This strategy represents a new means to activate alcohols as a cross-coupling partner. The convenient preparation of glycosyl esters and their stability exemplifies the potential of this method in medicinal chemistry.

Veterans Affairs Low-vision Intervention Trial II: One-year Follow-up.

SIGNIFICANCE: One-year follow-up is recommended for patients with macular diseases to assess functional changes associated with disease progression and to modify low-vision (LV) treatment plans, if indicated. PURPOSE: The purpose of this study was to observe 255 patients with macular diseases who received LV rehabilitation (rehabilitation with a therapist) or basic LV services (LV devices dispensed without therapy) during Veterans Affairs Low-vision Intervention Trial II after the trial ended at 4 months until 1-year follow-up. METHODS: The primary outcome measure was visual ability measured with the 48-item Veterans Affairs Low-vision Visual Functioning Questionnaire. Mean visual ability scores for the treatment groups were compared from baseline to 4 months, 4 months to 1 year, and baseline to 1 year. Changes from baseline to 1 year were compared between the two groups. Predictors of changes in visual ability from 4 months to 1 year were assessed using linear regression. RESULTS: Both groups experienced significant improvement in all measures of visual ability from baseline to 1 year but lost visual reading ability during the observation period (LV rehabilitation group, -0.64 [1.2] logit; 95% confidence interval [CI], -0.84 to -0.44 logit; basic LV group, -0.63 [1.4] logit; 95% CI, -0.88 to -0.38 logit), and overall visual ability was lost in the LV rehabilitation group (-0.20 [0.8] logit; 95% CI, -0.34 to -0.06 logit). Loss of visual reading ability in both groups from 4 months to 1 year was predicted by reading ability scores at 4 months, loss of near visual acuity from 4 months to 1 year, and lower EuroQol-5D utility index scores; loss of overall visual ability in the LV rehabilitation group during the same time period was predicted by lower overall ability scores at 4 months. CONCLUSIONS: Visual ability significantly improved in all groups from baseline to 1 year. However, the loss of visual reading ability experienced by both groups from 4 months to 1 year reduced the benefit of the services provided.

Cobalt-Catalyzed Trifluoromethoxylation of Epoxides.

A catalytic ring-opening reaction of epoxides by nucleophilic trifluoromethoxylation of trifluoromethyl arylsulfonate has been developed based on the use of a cobalt catalyst. This reaction provides an efficient, simple route for directly construction of a wide range of vicinal trifluoromethoxyhydrins under mild conditions. In addition, this method can convert terminal epoxides into target products with good chemo- and regioselectivity.

Pd(II)-NHDC-Functionalized UiO-67 Type MOF for Catalyzing Heck Cross-Coupling and Intermolecular Benzyne-Benzyne-Alkene Insertion Reactions.

A novel palladium N-heterocyclic bis-carbene dicarboxylate ligand (Pd-NHDC-H2L) was successfully synthesized. In addition, an Pd-NHDC-containing UiO-67 type MOF (UiO-67-Pd-NHDC) was prepared on the basis of a size-matched ligand mixture of biphenyl-4,4'-dicarboxylic acid/Pd-NHDC-H2L (9/1) and ZrCl4 under solvothermal conditions. The obtained UiO-67-Pd-NHC MOF can be a highly heterogeneous catalyst to promote Heck cross-coupling and intermolecular benzyne-benzyne-alkene insertion reactions.

Hetero Diels-Alder reactions of isolable N-borylenamines.

A new strategy for N-borylenamines by reaction of 2-alkynyl benzyl azides with B(C6F5)3 was developed. This novel 1,3-carboboration reaction proceeded via a 5-exo-dig cyclization/formal 1,1-carboboration/B(C6F5)2 shift reaction sequence. Additionally, N-borylenamines can undergo hetero Diels-Alder (HDA) reactions with a variety of dienophiles. Our results are an attractive complement to HDA reactions.

From trihydroborates to bisborylenes: a route to dinuclear bisborylene complexes.

A new route for the synthesis of dinuclear bisborylene complexes was described. A series of novel diruthenium bisborylenes were prepared through unprecedented triple B-H oxidative addition of trihydroborates with concomitant hydrogen liberation. Conversion of trihydroborates to bisborylenes involved the formation of tris(σ-B-H) borate as the crucial intermediate stage.

Ruthenium tris(σ-B-H) borate complexes: synthesis, structure, and reactivity.

The coordination of the B-H bond to a transition metal is fundamentally intriguing due to its connection with the transition metal-mediated B-H bond activation mechanism and catalysis. Most of the reported examples are σ-borane/borate complexes containing one or two σ-B-H bonds. However, examples of compounds containing three σ-B-H bonds are still much rarer. Herein, we report a facile approach for the synthesis of rare transition metal tris(σ-B-H) borate complexes by the salt elimination protocol using [Cp*RuCl]4 and lithium trihydroborates Li[ArBH3] containing 2,6-disubstituted aryl groups. These complexes have remarkable thermal stability in solution. In addition, this novel class of compounds has the unusual σ-complex that features three labile σ-B-H bonds. Our studies on these new species demonstrate that the coordination σ-B-H bond can undergo H/D exchange with D2 and ligand substitution reactions with PPh3, PCy3 and IPr2Me2. These results provide new approaches for the synthesis of both tris(σ-B-H) borates and bis(σ-B-H) borates.

A clinician's guide to patient selection for watchful waiting management of inguinal hernia.

OBJECTIVE: The goal of this study was to assist surgeons in managing patients with minimally symptomatic inguinal hernia by identifying characteristics that predict crossover to surgery or worsening of hernia symptoms. BACKGROUND: Randomized trials have suggested that watchful waiting management of minimally symptomatic inguinal hernia is an acceptable alternative to surgical repair. However, these trials found that roughly a quarter of patients would elect for repair in the first 2 years, suggesting that not all patients are good candidates for watchful waiting. METHODS: The 336 patients randomized to watchful waiting in the American College of Surgeons Watchful Waiting Hernia Trial constituted the study population. Preoperative patient characteristics were used to predict 2 outcomes, either crossover to surgery or the development of hernia pain limiting activities and/or crossover to surgery. Patients in our study were part of a previously registered randomized trial: NCT00263250. RESULTS: At 2 years, 72 patients crossed over to surgery, with pain with strenuous activities [odds ratio (OR), 1.3 per 10-mm visual analog scale pain scale], chronic constipation (OR, 4.9), prostatism (OR, 2.9), being married (OR, 2.3), and good health [OR, 3.0 American Society of Anesthesiologists Class (ASA) 1 vs 2], predicting crossover. An additional 28 patients developed pain, limiting their activities, with pain during strenuous activities (OR, 1.3 per 10-mm visual analog scale) and chronic constipation (OR, 4.5), predicting the combined outcome of pain limiting activities and/or crossover to surgery. Higher levels of activity reduced the risk (OR, 0.95) of this combined outcome. CONCLUSIONS: Readily identifiable patient characteristics can predict those patients with minimally symptomatic inguinal hernia who are likely to "fail" watchful waiting hernia management. Consideration of these factors will allow surgeons to optimally tailor hernia management.

Synthesis of C-acyl furanosides via the cross-coupling of glycosyl esters with carboxylic acids.

C-Acyl furanosides are versatile synthetic precursors to a variety of natural products, nucleoside analogues, and pharmaceutical molecules. This report addresses the unmet challenge in preparing C-acyl furanosides by developing a cross-coupling reaction between glycosyl esters and carboxylic acids. A key step is the photoredox activation of the glycosyl ester, which promotes the homolysis of the strong anomeric C-O bond through CO2 evolution to afford glycosyl radicals. This method embraces a large scope of furanoses, pyranoses, and carboxylic acids, and is readily applicable to the synthesis of a thymidine analogue and diplobifuranylone B, as well as the late-stage modification of (+)-sclareolide. The convenient preparation of the redox active glycosyl ester from native sugars and the compatibility with common furanoses exemplifies the potential of this method in medicinal chemistry.

B-H and O-H bonds activation via a single electron transfer of frustrated radical pairs.

The rare examples of B-H bond activation in a frustrated radical pair regime have been observed by treatment of TEMPO radicals with Piers' borane HB(C6F5)2 or bis-borane, respectively. The resulting concomitant formation of zwitterionic products and geminal N/B frustrated Lewis pairs implied a one electron process. In addition, the reaction of a TEMPO/B(C6F5)3 pair with H2O·B(C6F5)3 was assumed to involve one-electron reduction of water. Our results provide insights into chemical bond (e.g. B-H and O-H) activation via a single electron transfer.

Facile synthesis of air-stable heterobimetallic osmium-silver hydride complexes.

The synthesis and characterization of air-stable heterobimetallic Os-Ag hydrides are described. All of the new heterobimetallic Os-Ag hydrides are neutral, and the in situ generated and presynthesized cis-[Os](H)-CC-R units in these frameworks act as organometallic bidentate chelating ligands coordinating with the AgPPh3 cation, which makes these complexes more stable. Our results provide a new synthetic route for the construction of stable heterobimetallic complexes.

Rivastigmine Transdermal Patch Treatment for Moderate to Severe Cognitive Impairment in Veterans with Traumatic Brain Injury (RiVET Study): A Randomized Clinical Trial.

Cognitive impairment is common in veterans with histories of traumatic brain injury (TBI). Cholinergic deficits have been hypothesized as contributors to this impairment. We report the effects of cholinesterase inhibitor rivastigmine transdermal patch treatment in veterans with TBI and post-traumatic memory impairment. Our objective was to evaluate the efficacy and safety of a 9.5 mg/24 h (10 cm2) rivastigmine patch in veterans of military conflicts with persistent moderate to severe memory impairment at least 12 weeks after TBI. This randomized, outpatient, double-blind, placebo-controlled 12-week trial with an exploratory double-blind phase of an additional 14 weeks was conducted at 5 VA Medical Centers, among veterans with closed, non-penetrating TBI who met or exceeded modified American Congress of Rehabilitation Medicine criteria for mild TBI with verbal memory deficits, as assessed by the Hopkins Verbal Learning Test, Revised (HVLT-R). Patients were randomized 1:1 to rivastigmine or matching placebo patches after a 1-week single-blind, placebo run-in phase. At randomization, patients received 4.6 mg/24 h rivastigmine patches or matching placebo increased to a 9.5 mg/24 h patch after 4 weeks. The primary efficacy outcome measure was the proportion of participants who had at least a five-word improvement on the HVLT-R Total Recall Index (Trials 1-3). A total of 3671 participants were pre-screened, of whom 257 (7.0%) were screened; 96 (37%) randomized, and 94 included in study analyses. Responder rates were 40.8% (20 of 49) and 51.1% (23 of 45) in the rivastigmine and placebo groups, respectively (p = 0.41). A mixed-effect model including treatment, time, and treatment-by-time interaction indicated no significant difference in treatment effect over time between the groups (p = 0.24). Overall, there were no significant differences in changes for all secondary outcomes between the rivastigmine and placebo groups. The most commonly observed adverse events were application site reactions. This trial provides the largest sample to date of veterans with TBI and post-traumatic memory deficits enrolled in a pharmacological trial. Trial Registration: clinicaltrials.gov Identifier: NCT01670526.

Plaque Regression and Endothelial Progenitor Cell Mobilization With Intensive Lipid Elimination Regimen (PREMIER).

BACKGROUND: Low-density lipoproteins (LDLs) are removed by extracorporeal filtration during LDL apheresis. It is mainly used in familial hyperlipidemia. The PREMIER trial (Plaque Regression and Progenitor Cell Mobilization With Intensive Lipid Elimination Regimen) evaluated LDL apheresis in nonfamilial hyperlipidemia acute coronary syndrome patients treated with percutaneous coronary intervention. METHODS: We randomized 160 acute coronary syndrome patients at 4 Veterans Affairs centers within 72 hours of percutaneous coronary intervention to intensive lipid-lowering therapy (ILLT) comprising single LDL apheresis and statins versus standard medical therapy (SMT) with no LDL apheresis and statin therapy alone. Trial objectives constituted primary safety and primary efficacy end points and endothelial progenitor cell colony-forming unit mobilization in peripheral blood. RESULTS: Mean LDL reduction at discharge was 53% in ILLT and 17% in SMT groups (P<0.0001) from baseline levels of 116.3±34.3 and 110.7±32 mg/dL (P=0.2979), respectively. The incidence of the primary safety end point of major peri-percutaneous coronary intervention adverse events was similar in both groups (ILLT, 3; SMT, 0). The primary efficacy end point, percentage change in total plaque volume at 90 days by intravascular ultrasound, on average decreased by 4.81% in the ILLT group and increased by 2.31% in the SMT group (difference of means, -7.13 [95% CI, -14.59 to 0.34]; P=0.0611). The raw change in total plaque volume on average decreased more in the ILLT group than in the SMT group (-6.01 versus -0.95 mm3; difference of means, -5.06 [95% CI, -11.61 to 1.48]; P=0.1286). Similar results were obtained after adjusting for participating sites, age, preexisting coronary artery disease, diabetes mellitus, baseline LDL levels, and baseline plaque burden. There was robust endothelial progenitor cell colony-forming unit mobilization from baseline to 90 days in the ILLT group (P=0.0015) but not in SMT (P=0.0844). CONCLUSIONS: PREMIER is the first randomized clinical trial to demonstrate safety and a trend for early coronary plaque regression with LDL apheresis in nonfamilial hyperlipidemia acute coronary syndrome patients treated with percutaneous coronary intervention. Registration: URL: https://www.clinicaltrials.gov. Unique identifier: NCT01004406 and NCT02347098.

Combining photoredox and silver catalysis for azidotrifluoromethoxylation of styrenes.

The first example of an azidotrifluoromethoxylation of styrenes has been achieved by synergistic visible-light-mediated photoredox and silver catalysis. Trifluoromethyl arylsulfonate (TFMS) and the Zhdankin reagent were used as the trifluoromethoxylation reagent and the azide source, respectively. A good functional group tolerance and mild reaction conditions of this method are applicable to late-stage azidotrifluoromethoxylation of complex small molecules. Furthermore, the mechanistic investigations indicate the single-electron transfer involved in the reaction.

Economic Evaluation of Low-Vision Rehabilitation for Veterans With Macular Diseases in the US Department of Veterans Affairs.

Importance: Examining costs and consequences of different low-vision (LV) programs provides important information about resources needed to expand treatment options efficiently. Objective: To examine the costs and consequences of LV rehabilitation or basic LV services. Design, Setting, and Participants: The US Department of Veterans Affairs (VA) Low Vision Intervention Trial (LOVIT) II was conducted from September 27, 2010, to July 31, 2014, at 9 VA facilities and included 323 veterans with macular diseases and a best-corrected distance visual acuity of 20/50 to 20/200. Veterans were randomized to receive basic LV services that provided LV devices without therapy, or LV rehabilitation that added a therapist to LV services who provided instruction and homework on using LV devices, eccentric viewing, and environmental modification. We compared costs and consequences between these groups. Interventions: Low-vision devices without therapy and LV devices with therapy. Main Outcomes and Measures: Costs of providing basic LV services or LV rehabilitation were assessed. We measured consequences as changes in functional visual ability from baseline to follow-up 4 months after randomization using the VA Low Vision Visual Functioning Questionnaire. Visual ability was measured in dimensionless log odds units (logits). Results: Of 323 randomized patients, the mean (SD) age was 80 (10.5) years, 314 (97.2%) were men, and 292 (90.4%) were white. One hundred sixty (49.5%) received basic LV services and 163 (50.1%) received LV rehabilitation. The mean (SD) total direct health care costs per patient were similar between patients who were randomized to receive basic LV services ($1662 [$671]) or LV rehabilitation ($1788 [$864]) (basic LV services, $126 lower; 95% CI, $299 lower to $35 higher; P = .15). However, basic LV services required less time and had lower transportation costs. Patients receiving LV rehabilitation had greater improvements in overall visual ability, reading ability, visual information processing, and visual motor skill scores.